JPH11300369A - Dephosphorizing device and dephosphorizing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make MAP grains in a reaction tower stationary by selectively extracting grown large-diameter grains from a tower and to continue stable and efficient operation over a long period. SOLUTION: A reaction tower 10 has a storage part 11 at the lowermost part, a small-diameter cylindrical classification part 12 above a storage part 11 and a large-diameter reaction part 13 above a classification part 12. A raw water inlet pipeline 21, a feed pipe 22 of a soln. of such a magnesium salt as MgCl2 , and a feed pipe 23 of an alkali agent such as NaOH are connected to the lower part of the reaction part 13. An inlet side of a circulating pipeline 25 is connected to the upper part of the reaction tower 10 and the outlet side to the lower part of a classification part 12. An overflow weir 15 is provided to the uppermost part of the tower 10, and a treated water discharge pipeline 27 is connected to the weir 15. An MAP grain extracting pipeline 26 is furnished to the bottom of the storage part 11, and fine MAP grain extracting pipelines 28, 29 and 30 are provided to the upper part of the reaction part 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for removing and recovering phosphorus in water containing phosphorus as MAP (magnesium ammonium phosphate), and in particular, to stabilize MAP particles in the apparatus to enable long-term continuous operation. To a dephosphorization device.

[0002]

2. Description of the Related Art Magnesium ions are added to phosphorus-containing water as a device for removing phosphorus from phosphorus-containing water such as sludge dewatered filtrate and digestion desorbed liquid generated in anaerobic and aerobic treatment processes such as sewage, human waste, and wastewater. Then, there is an apparatus for generating MAP from ammonia and phosphorus and magnesium contained in the water, and separating and recovering the generated MAP particles.

[0003] As one of the conventional dephosphorizers utilizing the MAP formation reaction, raw water is introduced into a lower portion of a reaction section of a reaction tower composed of a reaction section and a separation section below the reaction section, and treated water is removed. In some cases, the treated water is taken out from the upper part of the reaction tower and a part of the treated water is circulated from the upper part of the reaction tower to the lower part of the reaction part of the reaction tower by circulation means.

[0004] In this dephosphorization apparatus, the MAP particles are developed by a water flow rising in the reaction section. This rising water flow is a mixture of raw water and circulating water. When the height of the reaction section is about 2 to 3 m, the rising water flow including the raw water and the circulating water has an LV of about 30 to 60 m / hr. Appropriate. The grown MAP particles are withdrawn from the separation section at the bottom of the reaction tower. When extracting the MAP particles,
In order to stop the rising water flow and promote the settling of MAP particles,
Stop the flow once.

When the MAP particles recovered from the dephosphorizer are transferred, dehydrated, dried, or the like, it is desirable that the MAP particles have a large particle size of 1 mm or more.

[0006]

In the above-mentioned conventional dephosphorization apparatus, in order to stabilize the MAP particles in the reaction section,
It is necessary to preferentially extract particles that have grown larger than the separation unit, but it is difficult to classify MAP particles with a conventional dephosphorizer, so that such selective extraction is difficult. That is, the specific gravity of MAP is about 1.
7, the sedimentation velocity in the reaction zone was 1 m
Even a single particle of about m is about 300 m / hr. Actually, since the MAP particles associate with each other to form a particle group, the sedimentation velocity is lower than this. However, as described above, classification is performed at the time of sedimentation in the rising water flow in the reaction section of about LV 30 to 60 m / hr. However, as a result, the whole particles grow to a substantially uniform particle size.

For this reason, even when the MAP particles are being extracted, the growth of the particles is promoted, and the heavy particles that have grown to a large particle size exceeding 3 mm are immobilized at the lower part of the reaction tower, and the particles are fixed to each other to form a stone wall. To form things. In this case, it is necessary to stop the operation of the apparatus and withdraw a large amount of MAP particles in the reaction tower.

[0008] The present invention solves the above-mentioned conventional problems and provides a dephosphorization apparatus and a dephosphorization facility capable of stabilizing MAP particles in a reaction tower and continuing stable and efficient operation for a long period of time. The purpose is to provide.

[0009]

According to a first aspect of the present invention, in the dephosphorizer, raw water is introduced into a lower portion of a reaction tower, treated water is taken out from an upper portion of the reaction tower, and a part of water is removed from an upper portion of the reaction tower by a circulation means. In the dephosphorizer which circulates to the lower part of the reaction tower, a classification part having a horizontal cross-sectional area smaller than the horizontal cross-sectional area of the tower is provided at the lower part of the reaction tower, and a storage part is provided at the lower part of the classification part. Water is circulated through the classifying section by the circulating means.

In this dephosphorizer, since the circulating water is introduced into the classifying section having a small horizontal cross-sectional area, a large ascending flow velocity is formed in the classifying section, so that the MAP particles are effectively classified, and the particle size is reduced. Only the MAP particles having a large size settle in the storage section below the classification section. Then, the MAP particles can be efficiently extracted from the storage section.

That is, as described above, the height of the reaction tower is 2-3
m, L by liquid passing through the reaction tower (including circulating flow)
It is appropriate to set V to 30 to 60 m / hr in view of the residence time of raw water, but this LV cannot classify MAP particles grown to 1 mm or more. In the present invention, a classification section is provided at the lower portion of the reaction tower, for example, the horizontal cross-sectional area is set to 1/5 to 1/8 of the horizontal cross-sectional area of the reaction tower, and circulating water is flowed into the classification section. Is increased to 150 to 480 m / hr. With this LV, it is possible to classify MAP particles having a particle size of less than 5 mm. By adjusting the LV of this rising water flow,
For example, only the MAP particles of 3 mm or more are moved to the storage section,
MAP particles having a smaller particle size can be retained in the reaction section. As a result, it is possible to pull out particles having a large particle diameter, and to stabilize the MAP particles in the reaction section.

The dephosphorization equipment according to claim 2 is a dephosphorization device having a reaction tower, a seed crystal supply device, a particle supply means for extracting particles from the reaction tower and supplying the particles to the seed crystal supply device, A seed crystal supply means for supplying a seed crystal from the crystal supply device to the dephosphorization reaction tower.

[0013] In this dephosphorization equipment, MA is removed from the dephosphorization apparatus.
By pulling out the P particles and supplying seed crystals from the seed crystal supply device to the dephosphorization device, by forming a good particle size distribution of MAP particles in the reaction tower, the MAP particles in the reaction tower are reduced. Make it steady.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a dephosphorization apparatus and a dephosphorization facility of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a dephosphorizing apparatus 1 according to an embodiment.

In the reaction tower 10, the lowermost part is a storage part 11, and the upper part of the storage part 11 is a small-diameter cylindrical classification part 12, and the upper part of the classification part 12 is a large-diameter cylindrical reaction part 13. Has become. The top of the reaction tower 10 is open. A valve 11V is provided between the storage section 11 and the classification section 12.

In the lower part of the reaction section 13, an inlet pipe 21 for raw water (sewage, anaerobic digestion and desorbed liquid of night soil, phosphorus-containing water such as raw human waste), a magnesium salt solution such as MgCl ₂ (containing magnesium salt) And a supply pipe 23 for supplying an alkaline agent such as NaOH, and a diffuser pipe 24 for stirring. The supply pipe 23 is provided with a pump 23P interlocked with the pH meter 14 provided above the reaction tower 10.

An inflow side of a circulation pipe 25 is connected to an upper part of the reaction tower 1, and an outflow side of the circulation pipe 25 is connected to a lower part of the classification section 12. The piping 25 is provided with a circulation pump 25P and a flow meter 25F. Diffuser 2
In the case where 4 is provided, a granulating plate or a gas-solid separator (GSS) 16 is provided below the circulation pipe 25 on the inflow side.

A pipe 26 for extracting MAP particles is connected to the bottom of the storage section 11, and the pipe 26 is provided with a valve 26V. An overflow weir 15 is provided at the uppermost part of the reaction tower 10, and a pipe 27 for taking out treated water is connected to the overflow weir 15.

Further, at the same level as the inflow side of the circulation pipe 25 of the reaction tower 10 and 50 to 100 cm below it,
Exhaust particle extraction pipes 28, 29 and 30 are provided. The extraction pipes 28 and 29 are provided with valves 28 V and 29 V, respectively.
P is provided.

The pipe 31 is a water supply pipe for supplying transfer water when the MAP particles are withdrawn from the storage section 11.

The operation of the thus-configured dephosphorizer will be described below.

The reaction tower 10 is supplied with N through the supply pipe 23 so that the pH condition at which MAP precipitates, that is, pH 8-10.
An alkaline agent such as aOH is injected. When magnesium is insufficient for MAP precipitation, a magnesium salt solution such as MgCl ₂ is injected from the supply pipe 22.

In the reaction tower 10, the MA
MAP is granulated using the P particles as seed crystals. That is, the MAP particles are brought into a fluidized state by the inflow of the raw water and the circulation of the treated water, and new MAP is deposited on the surface of the MAP particles.
The MAP particles grow.

In the MAP precipitation process, when the phosphorus concentration of the raw water is high, there is a problem that MAP microcrystals are self-precipitated in the absence of seed crystals and large MAP particles cannot be obtained. In the phosphorus device, the treated water in the reaction tower 10 is extracted and circulated by the pipe 25 and the pump 25P, so that the phosphorus concentration in the MAP granulation reaction section in the reaction tower 10 can be reduced. Thereby, the reaction tower 1
The degree of supersaturation of MAP within 0 is reduced, and MAP does not self-precipitate as microcrystals but precipitates only on the surface of seed MAP particles and promotes the enlargement of MAP particles. The circulation of the treated water reduces the phosphorus concentration in the MAP granulation reaction section in the reaction tower 10 to a phosphate concentration of 100 mg / L or less, particularly 40 to 8 mg / L.
It is preferable to carry out so as to be 0 mg / L.

The treated water whose phosphorus concentration has decreased due to the precipitation of MAP rises in the reaction tower 10, passes through the overflow weir 15, and is discharged from the pipe 27.

The MAP particles coarsened in the reaction tower 10 are as follows:
In the present invention, the diameter (horizontal cross-sectional area) of the classification section 12 is small, and the rising flow rate of the circulating water flowing from the circulation pipe 25 is 100 m / min.
hr or more. For this reason, the MAP particles flow in the classification section 12, and the MAP particles
The particles are effectively classified, and only the MAP particles having a large particle diameter settle in the storage unit 11.

When the MAP particles have been accumulated in the storage section 11, the MAP particles in the storage section 11 are appropriately extracted. In this case, the valve 11V is closed, the valve 26V is opened, the transfer water is introduced from the pipe 31, and the MAP particles in the storage section 11 are extracted from the pipe 26. Thereby, only the MAP particles having a large particle diameter settled in the storage unit 11 can be extracted.

In the conventional dephosphorizer, when the MAP particles are pulled out during the steady operation, the liquid flow is temporarily stopped.
It was necessary to restart the flow again after the extraction of the MAP particles, which was disadvantageous in terms of the processing efficiency and the operation. However, with such a dephosphorizing apparatus of the present invention, the classification unit 12 and the storage unit 11 By closing the valve 11V during the period, the MAP particles can be pulled out while the liquid is kept flowing.

In such a dephosphorizer, if the balance between the number of MAP particles in the reaction tower and the amount of MAP precipitated in the reaction tower is lost due to the start-up of the apparatus, fluctuations in the quality of raw water, and the like, the dephosphorization apparatus may be installed in the reaction tower. A large amount of fine MAP particles are generated. The presence of such a large amount of fine particles indicates that M
In this case, the growth rate of the AP particles is reduced, and the efficiency of producing MAP particles having a large particle diameter is impaired.
If necessary, some of the fine MAP particles are extracted as extra particles from the pipes 27, 28, and 30.

In the dephosphorizer shown in FIG. 1, the angle of inclination of the tapered portion 12A, which is the transition from the small-diameter classifying portion 12 to the large-diameter reaction portion 13, with respect to the horizontal is 60 ° or more (for example, 60 to 75 °). ) Is preferable.

When the reaction section 13 and the classifying section 12 are cylindrical, the horizontal sectional area of the classifying section 12 is 1/5 or less, for example, 1/5 to 1/8 of the horizontal sectional area of the reaction section 13. Is preferred. With such a diameter ratio, the ascending flow velocity in the classifying section 12 is 100 m / hr or more, especially 12 m / hr.
It is preferably 0 m / hr or more, for example, 120 to 160 m / hr. In the case of this flow rate, MA having a particle size of 1-2 mm
The development rate of P particles is about 30 to 50%.

The inflow end of the circulation pipe 25 is preferably connected to a height of 100 cm or less (for example, 50 to 100 cm) from the liquid level in the reaction tower 10.

The connection between the pipes 22 and 23 is
It is preferable that the connection be made within 30 cm (for example, 10 to 30 cm) from the upper end of A. The raw water pipe 21 has a tapered portion 1
It is preferable that the connection be made within 20 cm (for example, 5 to 20 cm) from the lower end of 2A.

In the illustrated example, only the magnesium salt and the alkali agent are added. However, when the ammonia component is insufficient for the generation of MAP, ammonia or an ammonium salt is further added to the reaction tower.

In the present invention, the horizontal section of the reaction section and the classification section is not limited to a circle, but may be a square or a polygon.
These are preferably cylindrical.

According to such a dephosphorization apparatus, as described above, the MAP particles generated in the reaction section 13 are classified by the classification section 12, and the MAP particles having a large particle diameter are preferentially extracted from the storage section 11. The MAP particles in the reaction tower 10 can be stabilized, but even with such a dephosphorizer,
The amount of AP particles withdrawn and the MAP accumulated in the reaction zone
It is difficult to maintain a balance with the particle amount, and the steady state of the MAP particles may be disturbed.

The dephosphorization equipment according to claim 2 prevents such a problem by forcibly forming a good particle size distribution of the MAP particles in the reaction tower, and stabilizes the MAP particles in the reaction tower. It is intended.

Referring to FIG. 2 which shows an embodiment of the dephosphorization equipment of claim 2, the dephosphorization equipment of claim 2 will be described.

In the dephosphorization equipment shown in FIG.
1 is used, and members having the same functions are denoted by the same reference numerals.

The seed crystal tower 40 of the seed crystal supply device 2 shown in FIG.
The lower part is a small-diameter cylindrical storage part 41, the upper part of the storage part 41 is a large-diameter adjusting part 42, and the top part is open.

An overflow weir 43 is provided at the top of the seed crystal tower 40, and a discharge pipe 51 for surplus water is provided in the overflow weir 43. Further, a supply pipe 44 for supplying the crushed seed crystal is provided.

The inflow side of the circulation pipe 52 is connected to the upper part of the seed crystal tower 40, and the outflow side of the circulation pipe 52 is connected to the lower part of the storage part 41. The pipe 52 is provided with a circulation pump 52P, a flow meter 52F, and a valve 52V.

A valve 41V is provided at the bottom of the storage section 41.

A valve 53 for supplying a seed crystal to the reaction tower 10 of the dephosphorization device is provided below the adjusting section 42 of the seed crystal tower 40.
A pipe 53 having a V and a pump 53P is connected, and the pipe 53 is connected to the circulation pipe 25 of the reaction tower 10. Also, the MA extracted from the storage unit 11 of the reaction tower 10
A valve 54V for supplying P particles into the supply pipe 44
Is provided.

As described above, the operation in the case where the seed crystal supply device is provided in addition to the phosphorus removal device is as described above.

In the seed crystal supply device 2, when the seed crystals in the seed crystal tower 40 are insufficient, a part of the MAP particles extracted from the dephosphorization device 1 is pulverized and sieved. A material having a size of about 5 to 1 mm is introduced from a supply pipe 44 above the seed crystal tower 40. At this time, since fine crushed particles are generated, the fine crushed particles are stored in the storage section 41, and are appropriately extracted from the valve 41V.

In the circulation pipe 52, the adjusting section 4 of the seed crystal tower 40
The pump 52P is operated so that the flow velocity LV of Step 2 becomes 20 to 30 m / hr.

The seed crystals in the seed crystal tower 40 are supplied from the seed crystal supply pipe 53 to the circulation pipe 25 of the reaction tower 10 of the dephosphorizer 1.

When the particle size of the MAP particles withdrawn from the storage section 11 of the reaction tower 10 of the dephosphorizer 1 is not sufficiently large, the MAP particles are supplied to the seed crystal tower 40 through a pipe 54.

When the MAP particles are withdrawn from the reaction tower 10 of the dephosphorization apparatus 1 (at the end of or at the start of the drawing), a seed crystal having a particle size smaller than that of the extracted MAP particles is formed at the interface of the reaction tower 10. The MAP particles are supplied when the number of MAP particles in the reaction section 13 is decreased when the number of MAP particles is reduced, and a particle size distribution of MAP particles is formed in the reaction section 13.

The supply amount of the seed crystal is as follows, where d _{1 is} the particle size of the extracted MAP particles and d ₂ is the particle size of the seed crystal to be supplied.
It is preferable to set the drawing amount of the MAP particles × (d ₂ / d ₁ ) ³ so as to supply the seed crystal particles as many as the number of the drawn MAP particles.

In the dephosphorization equipment shown in FIG. 2, one decrystallizing device 1 is provided with one seed crystal supply device 2 in parallel. The seed crystal may be supplied to the dephosphorization device.

With such a dephosphorization facility, the MAP particle size distribution is formed in the reaction tower of the dephosphorization device, and the MA
Steady stabilization of the P particles can be ensured, and a more stable operation can be continued.

[0055]

The present invention will be described more specifically with reference to the following examples.

Example 1 Raw water having the following water quality was treated by the dephosphorizer shown in FIG.

[Raw water quality] PO ₄ -P: 100 ppm NH ₄ -N: 500 ppm pH: 6.0 The specifications and operating conditions of the dephosphorizer are as follows.

[Apparatus Specifications] Reaction tower: 150 mmφ × 3000 mmH (including the classification part, excluding the storage part) Classification part: 60 mmφ × 500 mmH Circulation pipe: The inflow end is located 500 mm below the liquid level of the reaction tower. Raw water supply amount: 180 L / hr Circulating water amount (rising flow rate): LV ³⁰ to 50 m / hr at superficial velocity Air amount: 0.4 Nm ³ / hr MgCl ₂ addition amount: 1 wt% MgCl ₂ aqueous solution and raw water PO ₄ -P concentration NaOH addition amount: A 2% by weight NaOH aqueous solution was added so that the overflow water pH became 8.2. As the MAP particles in the reaction section grew, the amount of circulating water was increased. The solution was gradually increased, and a liquid passing test for about 2 months was performed.

The MAP particles stored in the storage section were pulled out, and about 100 MAP particles were used as a sample to observe the shape and measure the particle size. As a result, MA
The shape of the P particles was nearly spherical and had a substantially uniform particle size. When the relationship between the number average particle size Σ (nd) / Σn and the empty tower LV in the classification part at that time was examined, the result shown in FIG. 3 was obtained. It was confirmed that the particle size of the MAP particles increased.

When the MAP particles in the reaction zone were observed, the particle size was clearly smaller than that in the storage zone.

From these results, it was confirmed that the MAP particles in the reaction section could be stabilized by providing a classification section and a storage section and forming an appropriate rising water flow in the classification section.

[0062]

As described above in detail, according to the dephosphorization apparatus and the dephosphorization equipment of the present invention, the MAP particles in the dephosphorization apparatus are stabilized, and a stable and efficient treatment is performed for a long time. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a dephosphorization apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a dephosphorization facility according to an embodiment of the present invention.

FIG. 3 shows the classification section empty tower SV and MAP showing the results of Example 1.
4 is a graph showing the relationship between the number average particle diameter of particles.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dephosphorization apparatus 2 Seed crystal supply apparatus 10 Reaction tower 11 Storage part 12 Classification part 13 Reaction part 25 Circulation piping 40 Seed crystal tower 41 Storage part 42 Adjustment part

Claims (2)

[Claims] 1. A dephosphorizer for introducing raw water into a lower portion of a reaction tower, removing treated water from an upper portion of the reaction tower, and circulating a part of water from an upper portion of the reaction tower to a lower portion of the reaction tower by a circulating means. A classifier having a horizontal cross-sectional area smaller than the horizontal cross-sectional area of the tower is provided at the lower part of the reaction tower, and a storage part is provided at a lower part of the classifier, and water is circulated to the classifier by the circulating means. A dephosphorization apparatus characterized in that the dephosphorization is performed. 2. A dephosphorization apparatus having a reaction tower, a seed crystal supply apparatus, a particle supply means for extracting particles from the reaction tower and supplying the particles to the seed crystal supply apparatus, and a dephosphorization method using the seed crystal supply apparatus. A phosphorus supply means for supplying a seed crystal to a reaction tower.