JP3160057B2 - Stirring aeration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to sewage treatment, human waste treatment,
The present invention relates to a stirring and aeration device used for performing aerobic biological treatment such as sludge treatment.

[0002]

2. Description of the Related Art Conventionally, among biological treatments, there are two types of aerobic treatments and anaerobic treatments in a floating biological treatment method, and treatment processes are assembled independently or in combination. In the case of aerobic treatment, oxygen is supplied to the mixture of activated sludge and raw water, and aerated from the bottom of the aeration tank with a diffuser or agitated with a stirrer to maintain the dissolved oxygen concentration at 1 to 3 mg / l. A system using a stirring and aeration device in combination with a porcelain is adopted. However, if an air diffuser made of ceramics having a small pore size, which is expected to have oxygen dissolving performance by aerobic treatment, is used, there is a problem that the air diffuser is likely to be clogged. Therefore, a stirring and aerator having been combined with a stirrer and an air diffuser having a large pore diameter which is unlikely to cause clogging has been put to practical use. The performance of such a stirring and aeration apparatus is as follows. When the depth of the aeration tank or the stirring tank is 5 m, and when the stirrer is efficiently designed as an axial flow or a mixed flow pump, air is aerobically treated and air is diffused into the diffuser. Supply dissolved oxygen concentration 1-3mg
To a / l is generally powered excluding air power 1 m ³ per aeration tank water is 0.04～0.05Kw, the oxygen transfer efficiency to Shimizu is about 30%. If the entire stirring and aerator is a submersible aerator that is installed at the bottom of the aeration tank, the drive shaft, which is composed of an electric motor and a speed reducer, can be directly connected to the pump impeller. Problems with insulation and maintenance. In the case of an underwater aerator, the air blowing position is located on the upstream side of the pump impeller. Therefore, the pump efficiency is greatly reduced due to air bubbles, and the required power and the stirring effect are greatly changed depending on the presence or absence of air blowing.

[0003]

In order to make up for the drawbacks of the submersible aerator, a motor unit is installed outside the tank and connected to an axial impeller placed in the tank via a drive shaft. An aerator configured to blow air to the downstream side has been proposed, but in the case of this aerator,
The axial impeller, air blowing, and means for atomizing the blown air are not suitable, and have problems such as vibration or large air bubbles flowing backward to the pump suction side. In addition, it is important for the axial impeller to apply a uniform dynamic pressure in the radial direction and to give a reasonable flow.However, in order to secure a large flow rate at a low head, a propeller type axial impeller is conventionally used. Although it is used, it cannot apply a constant dynamic pressure in the radial direction because the hub ratio is small and the blade height is large (because it is long in the radial direction), and a load acts on the blade tip. In addition to the lowering of the manufacturing cost, there is a problem that vibration is easily caused and the manufacturing cost is increased.

[0004]

SUMMARY OF THE INVENTION The present invention provides a stirring aeration apparatus which can reduce air bubbles with less power, enhance stirring and dispersing effects, improve oxygen dissolving efficiency, and reduce vibration. The vertical cylinder 2 is provided in the water in the processing tank 1, and the rotating shaft 4 rotated by the driving device 3 is positioned above the center of the vertical cylinder 2. An axial impeller 5 for generating a downward flow in the vertical cylindrical body 2 and a centrifugal impeller 6 located below the axial impeller 5 are fixed to the rotating shaft 4 and shrunk downward. A conical air distributor 7 having a diameter is disposed at a lower portion of the centrifugal impeller 6 at a central portion in the vertical cylinder 2, and a rectifying plate 8 is interposed between the vertical cylinder 2 and the air distributor 7. , Diffuser 9
Is fixed to the upper end of the air distributor 7, an air supply pipe 11 is connected to the air distributor 7, and the outer diameter of the centrifugal impeller 6 and the outer diameter of the boss 15 of the axial flow impeller 5 are fixed. And the outer diameter of the diffuser plate 10 are made substantially equal.

[0005]

1 to 5 show a stirring aeration apparatus according to an embodiment of the present invention. In biological treatment, air is blown into a mixed liquid of activated sludge and raw water while stirring.
In addition, a vertical cylindrical body 2 made of a cylindrical body is arranged and fixed in water in a processing tank 1 formed of an aerobic processing aeration tank for supplying oxygen to perform processing. A support table 18 is placed and fixed at the center of the
A bearing box 19 connected to a driving device 3 composed of an electric motor is fixed to the vertical shaft 2 connected to an output shaft of the driving device 3 via a shaft coupling 20. An axial impeller 5 that is arranged on the line and generates a downward flow in the vertical cylindrical body 2 above the rotary shaft 4 in the vertical cylindrical body 2, and a centrifugal wheel located below the axial flow impeller 5. A conical air distributor 7, to which the impeller 6 is fixed and whose diameter decreases downward, is arranged at the lower part of the centrifugal impeller 6 in the center of the vertical cylindrical body 2.

A plurality of vertical current plates 8 are arranged at equal angular intervals between the vertical cylinder 2 and the air distributor 7, and each current plate 8 is fixed to the vertical cylinder 2 and the air distributor 7. A diffuser plate 10 having a plurality of diffuser holes 9 having a diameter of 5 to 8 mm is fixed to an upper end of the air distributor 7, and the axial impellers 5 are fixed to a hub 15 at four or more angular intervals. The outer diameter of the hub 15 of the axial impeller 5, the outer diameter of the centrifugal impeller 6, and the outer diameter of the diffuser plate 10 are set to be the same or substantially equal.

At the upper end of the vertical cylindrical body 2, a frusto-conical suction port 12 expanding upward is continuously provided, and a plurality of vertical guide blades 13 are provided above the circumference of the suction port 12. A diffuser 14 is provided at an interval and extends downward at the lower end of the vertical cylindrical body 2. The air supply pipe 11 of the low-pressure blower 20 provided outside the processing tank 1 is provided with a diffuser 14. It is connected in the air distributor 7.

The outer diameter D _{1 of the} hub 15 and the axial impeller 5
When the ratio D ₁ / D ₂ to the outer diameter D ₂ of the blade 16 is smaller than 0.4, the axial flow pump comprising the axial flow impeller 5 rotated by the driving device 3 and the vertical cylindrical body 2 is used. Efficiency is reduced,
In addition, vibration is easily generated. Therefore, it is preferable to set the value of D ₁ / D ₂ to 0.4 or more, for example, 0.5.

An axial pump flow path 21 is provided between the axial impeller 5 and the air distributor 7 and the vertical cylindrical body 2, a drain hole 22 is provided at a lower end of the air distributor 7, and an air supply pipe 11 is provided. In order to prevent the air supplied into the air distributor 7 from coming out of the drain hole 22, the air diffusion hole 9 has a resistance smaller than the height H of the air distributor 7.

A plurality of notches 23 for shearing air bubbles released from the air diffusing holes 9 are provided in the centrifugal impeller 6 fixed to the rotating shaft 4 below the axial impeller 5, and the centrifugal impeller A plurality of blades 24 are fixed around the lower surface of the air diffuser 6, and air bubbles rising from the air diffusion holes 9 of the air diffusion plate 10 are sheared by the centrifugal impeller 6 to be finely divided, and then together with the mixed liquid in the circumferential direction. Are distributed. Further, the centrifugal impeller 6 induces a flow between the suction portion of the centrifugal impeller 6 and the axial pump flow path 21, and the fine air bubbles mixed with the flow cause the swirling flow from the axial flow impeller 5. By colliding with the air bubbles, the air bubbles are further refined and the effect of dispersing the air bubbles is further increased, so that the oxygen dissolving ability is greatly improved. Furthermore, since the air bubbles can be sheared and miniaturized, the rising speed of the air bubbles is reduced, and backflow to the suction port side of the axial flow pump is prevented, so that vibration of the axial flow pump can be reduced.

The axial flow pump is most suitable for sending a large amount of liquid. However, in the case of the present invention, since the head is low, the head loss in the flow path of the suction port 12, the vertical cylinder 2, and the diffuser 14 is reduced. It is important to make it as small as possible.

As described above, the hub 15 of the axial impeller 5
If the outer diameter of the centrifugal impeller 6 and the outer diameter of the air diffuser plate 10 are set to be the same or substantially equal to each other, it is possible to minimize the performance deterioration of the axial pump. Also, if air is supplied to the air distributor 7 at a depth of 1.5 to 3 m from the water surface, air can be sent by the low-pressure blower 20, and therefore, compared to the case where a submersible aerator is installed at the bottom in the aeration tank. Since the air supply pressure may be about 1/2, a further energy saving effect can be exhibited.

When a stirring aeration apparatus is installed in the processing tank 1 consisting of an aeration tank or a stirring tank, when the processing tank 1 is rectangular, the arithmetic mean value of the short side and the long side of the peripheral wall of the processing tank 1 is calculated by the diameter D.
When the processing tank 1 is circular, the inner diameter is set to the diameter D.
And the ratio D / D of the diameter D to the inner diameter D ₃ of the vertical cylinder 2
₃ was set to 3 to 10, the distance L ₁ from the water surface to the upper end of the suction port 12 is set to 1.3 to 1.7 times the internal diameter D _3,
And the distance L ₂ from the bottom surface of the processing tank 1 to the lower end portion of the diffuser 14 is set to 2.0 to 2.5 times the internal diameter D _3, and the position of the agitating aeration apparatus, the processing bath 1 is rectangular In some cases, the diagonal of the processing tank 1 intersects and the processing tank 1
When is set to the center of the processing tank 1, the best performance is exhibited.

The outer diameter of the blade 16 of the axial impeller 5 is D
₂ , when the outer diameter of the hub 15 of the axial impeller 5 is D ₁ and the inner diameter of the vertical cylinder 2 is D ₃ , D ₂ / D ₃ is 0.96 to 0.9.
In 8, D ₁ / D ₂ of 0.5 or more, the specific rate 2200-28
When set to 00 [RPM · (m ³ / min) ^1/2 · m ^−3/4 ], excellent performance is exhibited.

Next, a description will be given of a test example performed using the stirring aeration apparatus of the present invention. When a test was conducted by installing a stirring and aerator in the center of the rectangular concrete treatment tank 1 having a depth of 5 m, a short side of 5 m, and a long side of 7 m, the performance shown in Table 1 could be obtained for the fresh water. .

[Table 1]

[0016]

According to the present invention, the air bubbles rising from the air distributor 7 through the air diffusion holes 9 of the air diffusion plate 10 are sheared by the rotating centrifugal impeller 6 to be finely divided, and the fine particles are mixed with the mixed liquid. The flow can be dispersed in the circumferential direction of the centrifugal impeller 6, and the centrifugal impeller 6 induces a flow between the suction portion of the centrifugal impeller 6 and the axial flow pump channel 21, and the fine particles mixed into this flow By the air bubbles colliding with the swirling flow from the axial impeller 5,
Since the air bubbles are further refined and the dispersing effect is further enhanced, the oxygen dissolving ability can be greatly improved, and the air bubbles are further refined. Backflow to the suction port side can be prevented, vibration of the stirring and aerator can be reduced, and the outer diameter of the hub 15 of the axial impeller 5 and the centrifugal impeller 6 can be reduced.
Outer diameter and air diffuser plate 1 above air distributor 7
0 is almost equal to the outer diameter of the axial flow pump flow path 2.
1 can be operated with small power by reducing the resistance.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing a stirring and aerator according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional side view showing a part of FIG. 1 in an enlarged manner.

FIG. 3 is an enlarged longitudinal side view showing a part of FIG. 2;

FIG. 4 is a side view showing a centrifugal impeller.

FIG. 5 is a bottom view showing the centrifugal impeller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing tank 2 Vertical cylinder 3 Drive 4 Rotating shaft 5 Axial impeller 6 Centrifugal impeller 7 Air distributor 8 Rectifier plate 9 Diffusion hole 10 Diffusion plate 11 Air supply pipe 12 Suction port 13 Guide blade 14 Diffuser 15 Hub 16 Blade Reference Signs List 17 cover material 18 support base 19 bearing box 20 low-pressure blower 21 axial pump flow path 22 drainage hole 23 cutout hole 24 blade

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-112893 (JP, A) JP 2-39959 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 3/14-3/26 B01F 3/04 B01F 7/16

Claims (2)

(57) [Claims] 1. A vertical cylindrical body 2 is provided in water in a processing tank 1,
A rotary shaft 4 rotated by a driving device 3 is disposed above a central portion of the vertical cylinder 2, and an axial impeller 5 for generating a downward flow in the vertical cylinder 2 is provided on the rotary shaft 4. A centrifugal impeller 6 positioned below the axial impeller 5 is fixed, and a conical air distributor 7 whose diameter is reduced downward is attached to a central portion of the vertical cylindrical body 2 at a lower portion of the centrifugal impeller 6. The air distributor 7 is interposed between the vertical cylindrical body 2 and the air distributor 7, and a diffuser plate 10 having a diffuser hole 9 is fixed to the upper end of the air distributor 7. The air supply pipe 11 is connected inside, and the outer diameter of the centrifugal impeller 6 is
A stirring and aeration device in which the outer diameter of the boss 15 of the axial impeller 5 and the outer diameter of the diffuser plate 10 are substantially equal. 2. An upper end portion of the vertical cylindrical body 2 is provided with a suction port 12 expanding upward, and a guide blade 13 is provided at an upper portion around the suction port 12, and a lower end of the vertical cylindrical body 2 is provided. In the department,
A diffuser (14) that expands downward is provided, and the number of blades (16) of the axial impeller (5) is four or more.
Stirring aeration equipment.