JPH0833896A - Axial-flow impeller in agitated aerator - Google Patents

Abstract

PURPOSE:To provide the axial-flow impeller of an agitated aerator capable of solving poblems such as the back blow, blow-by and flooding of bubbles, vibration and noise by making the axial water current strength uniform in any position in the radial direction of the impeller. CONSTITUTION:This agitated aerator is provided with a draft tube 5 vertically arranged in a treating tank 4, an axial-flow impeller 6 positioned in the tube 5 and rotated by a motor 1 through a driving shaft 2, an air diffuser pipe 3 arranged below the impeller 6 and connected to a blower 8 and a flow straightening member 7 arranged below the diffuser pipe 3. Further, plural blades 9 constituting the impeller 6 have the pitch uniform at any position in the radial direction or gradually increasing from the tip toward the root.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stirring and aeration apparatus used for treating sewage such as sewage and human waste and sludge, and more particularly to improvement of an axial impeller in the apparatus.

[0002]

2. Description of the Related Art As one method for aerobically treating sewage with activated sludge, as shown in FIG. 1, a draft tube (5) vertically arranged in a treatment tank (4) and a draft tube (5). Located inside (5) and driven by motor (1)
An axial impeller (6) rotated through (2), an air diffuser (3) located below the axial impeller (6) and connected to a blower (8), and an air diffuser (3) Rectifying member arranged under
(7) Using an agitating aerator equipped with
(6) creates a downward flow in the draft tube (5),
There is a stirring and aeration system in which the liquid to be treated is agitated while being aerated by blowing air into the liquid.

As an investigation of the axial impeller of the stirring and aerating device used in this system, each blade (9) is required from the centrifugal direction to the half rotation direction in order to prevent the entanglement of the fibers in the wastewater due to the stirring. Angle-tilted (that is, receded) axial impeller (Japanese Patent Laid-Open No. 60-227821)
No.), or to increase the boss ratio to prevent backflow (flooding) of vibration or coarse bubbles to the suction side, or to install a small disc-shaped centrifugal impeller under the axial flow impeller to disperse the bubbles. Stirrer
253592) is known.

[0004]

The impeller of such a conventional stirring and aeration apparatus is a two-dimensional impeller (impeller with a constant attack angle) and a large boss ratio. Therefore, it is desirable that the axial water flow strength during stirring is uniform at any position in the radial direction of the impeller.
The water flow is strong on the outer peripheral side of the impeller, and extremely weak on the side near the boss, and is unevenly biased toward the outer peripheral side. As a result, a bubble pool occurs around the boss below the propeller, causing backflow of bubbles (flooding), vibration,
Noise is generated, and in order to discharge the air bubbles generated in this way from the inside of the draft tube, it is necessary to further increase the rotation speed and increase the downward water amount by using excess power, and the effective working area of the impeller is small. In addition, there is a problem that a large diameter (for large capacity) impeller is required compared to the amount of water, and it is difficult to perform efficient and stable operation of the device.

In view of the above points, an object of the present invention is to make backflow blowout of air bubbles (flooding) by making the axial water flow strength at the time of stirring uniform and non-uniform at each position in the radial direction of the impeller. ), It is to provide an axial flow impeller of a stirring and aerating device capable of solving problems such as vibration and noise.

[0006]

A first type of axial impeller according to the present invention is a draft tube (5) vertically arranged in a treatment tank (4) and a draft tube (5) located in the draft tube (5). , And an axial flow impeller (6) rotated by the motor (1) via the drive shaft (2), and an air diffuser (below the axial flow impeller (6) and connected to the blower (8) ( 3) and a rectifying member (7) arranged below the air diffusing pipe (3), in a stirring and aerating device, a plurality of blades (9) constituting the axial impeller (6) are It is characterized by having a constant pitch at any position or having a pitch that gradually increases from the tip toward the root.

A preferable example of an impeller having a constant pitch is an impeller used at an outer peripheral speed of 15 m / s to 5 m / s, and a pitch ratio (blade pitch P / blade diameter D) of 0.500.
(Attack angle θ (R1.0) = about 9.0 ° to θ (R0.1
8) = about 41.5 °) to pitch ratio 1.200 (angle of attack θ)
(R1.0) = about 20.1 ° to θ (R0.18) = 6
It is in the range of 4.8 °).

A preferable example of the impeller having a pitch that gradually increases from the tip to the root is an outer peripheral speed of 15 m / s.
An impeller used at 5 m / s, in which the pitch gradually increases from the tip pitch ratio of 0.5 toward the root, and the pitch ratio is 1.200 near the boss.

[0009]

(Equation 1) θ (R1.0) indicates the angle of attack at the tip of the blade, and θ
(R0.18) indicates the angle of attack near the boss.

The second axial flow impeller has a width (that is, a width at which the plurality of blades (9) forming the axial flow impeller (6) gradually increase from the tip to the root (that is, at the tip). The width is narrowed toward the end).

Further, the third axial flow impeller has a plurality of blades (9) constituting the axial flow impeller (6) in the agitating and aerating device having the above-mentioned structure, which is constant at any position in the radial direction. Alternatively, it has a pitch that gradually increases from the tip to the root, and has a width that gradually increases from the tip to the root. The pitch means one round (3 turns in the circumferential direction of the drive shaft or the axis of the drive shaft.
60 °) The distance traveled in the axial direction when traveling.

The boss ratio (boss diameter Db / blade diameter D) can be reduced to 18% if necessary (the conventional boss ratio was about 50%). As a result, power efficiency can be improved by 15% or more (aeration efficiency is improved by about 15% and water supply efficiency is improved by about 10%).

Further, in order to improve the stirring efficiency of the blade (9), it is also preferable to perform blade surface processing for improving the roughness.

[0014]

In the first axial flow impeller, the plurality of blades (9) constituting the axial flow impeller (6) are constant at any radial position or gradually increase from the tip to the root. The blades of the axial impeller (6) because they have a pitch
(9) is a high-skew (highly twisted) three-dimensional blade, in which the axial water flow strength during agitation is enhanced near the boss, and it is uniform and non-biased at any position in the radial direction of the impeller. Becomes As a result, problems such as backflow of bubbles (flooding), vibration, and noise are solved, and as a result, efficiency and stabilization of processing and power consumption are achieved.

Further, in the second axial flow impeller, since the plurality of blades (9) constituting the axial flow impeller (6) have a tapered width, the axial water flow strength at the time of stirring is also close to the boss. It is enhanced to be uniform and unbiased at any radial position of the impeller. This also solves the problems of bubble backflow (vibration), vibration, noise, etc., resulting in efficient and stable processing and power consumption.

Further, in the third axial flow impeller, the plurality of blades (9) constituting the axial flow impeller (6) are constant at any position in the radial direction, or as they go from the tip to the root. Since it has the gradually increasing pitch and the taper width, the above-mentioned effects are synergistically exhibited.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is an overall view showing an example of a stirring and aerating device. The stirring and aerating device is located inside the draft tube (5) and the draft tube (5) which are vertically arranged in the treatment tank (4), and is rotated by the motor (1) via the drive shaft (2). An axial flow impeller (6) and an air diffuser (3) located below the axial flow impeller (6) and connected to the blower (8),
It is provided with a rectifying member (7) arranged below the air diffuser (3). Using this device, a downward flow is formed in the draft tube (5) by the axial flow impeller (6), and air is blown into the draft tube to diffuse the liquid into the treatment tank (4). ). Air blower (8)
Is sent to the diffuser pipe (3) by the air, and the air discharged from the diffuser pipe is sheared by the downward flow due to the rotation of the axial flow impeller (6) into fine bubbles.

The fine bubbles are guided to the bottom of the tank together with the downward flow in the draft tube (5), and when rising from the bottom of the tank to the outside of the draft tube (5), an upward flow is generated in the liquid around the bubbles. Squeeze to facilitate liquid circulation in the processing tank (4).

The axial impeller (6) has three blades (9),
It has a low lift, a large capacity, and a small power, and a large stirring force can be obtained.

The diffuser pipe (3) is provided below the axial flow impeller (6) and ejects air at a right angle to the downward water flow.

The draft tube (5) has an inner diameter substantially equal to the diameter of the axial impeller, guides the liquid to be treated and bubbles to the bottom of the tank, strengthens the stirring power at the bottom, and enhances the air dissolution efficiency.

The rectifying member (7) is for efficiently converting the vortex flow formed by the axial flow impeller (6) in the draft tube (5) into a downward flow.

In the stirring and aerating device having this structure, the stirring mechanism and the aeration mechanism are independent of each other, so that the stirring intensity and the oxygen supply amount can be independently controlled.

FIG. 2 shows the structure of the axial flow impeller according to the present invention. The three blades (9) that make up the axial impeller (6) have a constant pitch at any radial position from the boss (10) (eg, points a, b, c, d, e in FIG. 2). It is a shape having. Here, as described above, the pitch is one revolution (360 mm) in the circumferential direction of the moving shaft or the axis of the moving shaft.
°) The distance traveled in the axial direction when moving. However, FIG. 2 shows the distance traveled in the axial direction when the pitch shape of the blade (9) is advanced around the 90 ° axis, that is, H / 4 (H = pitch).

3 and 4 are a plan view and a sectional view of the axial flow impeller, respectively. The axial impeller (6)
It has a width that gradually increases from the tip to the root. In this embodiment, the blade width at an arbitrary position (r) from the axis is as follows.

[0027]

[Table 1] Here, the blade width ratio is r / R = 0.7 (R is the impeller radius)
It is a value obtained by setting the blade width at 100%.

Although the example in which the blades (9) of the axial impeller (6) have a pitch that gradually increases from the tip to the root is not shown, the blade (9) of this shape has a pitch that increases toward the root or boss side. Stand up.

An impeller having a constant pitch or a pitch that gradually increases toward the boss side can enhance the water flow in the vicinity of the boss portion and average the axial movement amount of water at an arbitrary radius, whereby the bubble Backflow (flooding) can be suppressed.

FIG. 5 shows the number of revolutions of a conventional impeller having an equal width and an equal attack angle, an impeller of the present invention having an equal width and an equal pitch, and an impeller of the present invention having a tapered width and an equal pitch. It is a graph which shows the relationship with AHC (maximum supply air amount) efficiency.

The conventional impeller has a two-dimensional angle (constant angle of attack) shown in Table 1, and the impeller of the present invention is of the MAU type (Amagasaki Steel Co., Ltd.-correction blade of the Ministry of Transport) shown in Table 1. is there.

[0032]

[Table 2] From FIG. 5, it can be seen that the impeller according to the present invention produces a higher AHC efficiency, that is, a higher amount of dissolved air in water, as compared with the conventional product.

FIG. 6 (a) shows the axial flow impeller according to the present invention, and FIG. 6 (b) shows the strength of the water flow in the liquid circulation distribution when the above-mentioned conventional impeller is used, at the radial position perpendicular to the axis. It is shown. As is clear from the comparison between FIGS. 6 (a) and 6 (b), when the axial flow impeller according to the present invention is used, the strength of the water flow in the axial direction of the water is near the boss as compared with the conventional two-dimensional angular impeller. It greatly increases at and is averaged at any position in the radial direction of the wing (9).

[0034]

According to the present invention, the water flow strength in the axial direction at the time of agitation is enhanced near the boss, and it becomes uniform and non-biased at any position in the radial direction of the impeller. As a result, problems such as backflow of bubbles (flooding), vibration, and noise are solved, and as a result, efficiency and stabilization of processing and power consumption are achieved.

Further, it is possible to improve the oxygen dissolution efficiency in the liquid to be treated and thereby reduce the power consumption.

Furthermore, since the generation of vibrations and noises can be prevented as described above, the boss ratio can be greatly reduced, and thereby the stirring efficiency in the same cross section can be improved.

[Brief description of drawings]

FIG. 1 is an overall view showing an example of a stirring aeration apparatus.

FIG. 2 is a schematic view of a pitch shape of blades showing a structure of an axial flow impeller.

FIG. 3 is a plan view of an axial flow impeller.

FIG. 4 is a sectional view of an axial flow impeller.

FIG. 5 is a graph showing the relationship between the rotation speed and the AHC (maximum supply air amount) efficiency.

FIG. 6 is a liquid circulation distribution map.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Drive shaft 3 ... Air diffuser 4 ... Treatment tank 5 ... Draft tube 6 ... Axial flow impeller 7 ... Rectifying member 8 ... Blower 9 ... Blade 10 ... Boss

Claims (3)

[Claims] 1. A draft tube (5) vertically arranged in a treatment tank (4) and a draft tube (5),
And an axial impeller (6) rotated by the motor (1) via the drive shaft (2) and an air diffuser (3) located below the axial impeller (6) and connected to the blower (8). ) And the air diffuser
In a stirring and aerating device equipped with a rectifying member (7) arranged below (3), a plurality of blades (9) constituting an axial flow impeller (6) are fixed at any radial position. Or an axial impeller in a stirred aerator characterized by having a pitch that gradually increases from the tip to the root. 2. A draft tube (5) vertically arranged in the treatment tank (4), and a draft tube (5) located inside the draft tube (5),
And an axial impeller (6) rotated by the motor (1) via the drive shaft (2) and an air diffuser (3) located below the axial impeller (6) and connected to the blower (8). ) And the air diffuser
In a stirring and aerating device equipped with a rectifying member (7) arranged below (3), a plurality of blades (9) forming the axial impeller (6) have a width that gradually increases from the tip to the root. An axial flow impeller in a stirring and aerating device, comprising: 3. A draft tube (5) vertically arranged in the treatment tank (4), and a draft tube (5) located inside the draft tube (5),
And an axial impeller (6) rotated by the motor (1) via the drive shaft (2) and an air diffuser (3) located below the axial impeller (6) and connected to the blower (8). ) And the air diffuser
In a stirring and aerating device equipped with a rectifying member (7) arranged below (3), a plurality of blades (9) constituting an axial flow impeller (6) are fixed at any radial position. Or having a pitch that gradually increases from the tip to the root and has a width that gradually increases from the tip to the root, and an axial flow impeller in a stirring aerator.