JP2010167329A - Aeration agitator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aeration agitator where an aeration operation dissolving oxygen into water is performed at high efficiency, further, a sufficient oxygen dissolving rate at which oxygen is dissolved to water quantity is secured, and also, the clogging of an air supply port hardly occurs. <P>SOLUTION: In the aeration agitator where a cylindrical tube body 4 is arranged around a stirring shaft 3 fitted with an impeller 2, and a downward stream is generated in the inside of the tube body 4 by the impeller 2, the wall part of the tube body 4 on the downstream side of the impeller 2 is provided with an air supply port 51, and a blower mechanism 6 by which air is supplied to the outer circumferential part of the impeller 2 via the air supply port 51 is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an aeration stirrer, and in particular, performs aeration operation in which oxygen is dissolved in water with high efficiency, ensures a sufficient oxygen dissolution rate for dissolving oxygen with respect to the amount of water, and is less likely to cause clogging of air supply holes. The present invention relates to an aeration stirrer.

As an aeration stirrer that aerobically treats sewage with activated sludge, for example, there is one described in Patent Document 1 below.
As shown in FIG. 4, the aeration and agitation apparatus includes a draft tube 81 arranged vertically in the treatment tank 8, and an impeller that is located in the draft tube 81 and is rotated by a motor 82 via a drive shaft 83. 84, an air diffuser 86 disposed below the impeller 84 and connected to the blower 85, and a rectifying member 87 disposed below the air diffuser 86.
And this aeration stirrer forms the downward flow in the draft tube 81 with the impeller 84, and blows air in this, so that water is stirred while being diffused in the water to be treated.

  In order to prevent entanglement of fibers in the sewage due to agitation, an agitation device equipped with an impeller in which each blade is inclined at a required angle from the centrifugal direction to the rear of the rotation is studied as an impeller of such aeration agitation device. (Refer to Patent Document 2), and the boss ratio is increased for the purpose of preventing vibrations and backflow (flooding) of coarse bubbles to the suction side, or a small disc-shaped centrifugal impeller under the impeller to disperse bubbles. An attached stirrer (see Patent Document 3) is known.

Recently, however, the need for energy conservation and advanced treatment of sewage have been promoted, and a further increase in aeration efficiency that dissolves oxygen in water, specifically, energy saving is required, and at the same time, the efficiency of oxygen transfer power Therefore, it is required to increase it by 1.2 times or more.
In this case, it is necessary to make the bubbles of the aeration fine, but it is necessary to keep the air supply holes for supplying air into the water sufficiently large as in the conventional case.
In other words, since the air supply holes provided to blow air into the water are in the water, when the blower of the air supply source is stopped, sewage mixed with dust enters the air supply holes. There also arises a problem that dust blocks a part of the air supply holes and prevents the air from being discharged.

Japanese Patent No. 3239170 Japanese Patent Laid-Open No. 60-227821 Japanese Patent Laid-Open No. 5-253592

  In view of the problems of the above-described conventional aeration and agitation devices, the present invention performs an aeration operation for dissolving oxygen in water with high efficiency, ensures a sufficient oxygen dissolution rate for dissolving oxygen relative to the amount of water, and provides air supply holes. An object of the present invention is to provide an aeration stirrer that makes it difficult to cause clogging.

  In order to achieve the above object, the aeration stirrer according to the present invention has a cylindrical body disposed around a stirring shaft to which an impeller is attached, and the impeller generates a downward flow inside the cylindrical body. In the present invention, an air supply hole is provided in the wall portion of the cylindrical body around the impeller, and a blower mechanism for discharging air to the outer peripheral portion of the impeller through the air supply hole is provided.

  In this case, an air chamber can be provided around the cylinder at a position downstream of the impeller, and the air chamber and the inside of the cylinder can be communicated with each other through an air supply hole.

  In addition, a hollow rectifying plate that rectifies the swirling flow by the impeller in the cylinder axis direction is disposed on the downstream side of the impeller, and an air discharge hole is provided at a lower portion of the rectifying plate, and the cylindrical body is surrounded around the rectifying plate. An air supply hole can be provided in the wall, and a blower mechanism that supplies air to the inside of the current plate through the air supply hole can be provided.

  In addition, an air chamber can be provided around the cylindrical body at the position of the rectifying plate, and the air chamber and the inside of the rectifying plate can be communicated with each other through an air supply hole.

  Moreover, the cross-sectional shape of a baffle plate can be made into an ellipse or a blade | wing cross-sectional shape.

  Further, the diameter of the upper part of the cylinder is expanded in a bowl shape, and a disk is provided at a predetermined interval so as to face the enlarged diameter part, so that water flows in from the periphery in the radial inward direction of the cylinder. An inlet can be provided.

According to the aeration stirrer of the present invention, in the aeration stirrer in which the cylindrical body is disposed around the stirring shaft to which the impeller is attached, and the impeller generates a downward flow inside the cylindrical body, the periphery of the impeller The air supply holes are provided in the wall of the cylinder body, and a blower mechanism is provided to discharge air to the outer periphery of the impeller through the air supply holes. It is subdivided and enters into fine bubbles by entering the water stream.
That is, in the aeration stirrer of the present invention, since it is not necessary to make the air supply hole small in order to make the bubbles fine, the air supply hole is provided with a large diameter to prevent clogging, and near the impeller having a shallow water depth. By sending air into the water from the large-diameter air supply hole provided, the power of the blower can be reduced to save energy.
Since the fine bubbles subdivided by the water flow with a strong velocity gradient have lost buoyancy, they are carried together with the water flow to the bottom of the water tank and stay for a long time, and the fine bubbles have a larger surface area than coarse bubbles of the same volume. The oxygen dissolution rate can be increased due to the large contact area with the water, and as a result, a large percentage of the fine bubbles in the fine bubbles compared to the normal bubbles that reach the water surface when large amounts of oxygen move to the water due to large buoyancy. Of oxygen can be transferred to water.

  In addition, an air chamber is provided around the cylinder body at a position downstream of the impeller, and the air chamber and the inside of the cylinder body are communicated with each other through the air supply holes, so that the plurality of air supply holes can be easily surrounded around the impeller. Can be set. In this case, the radial position of the air supply hole is provided so as to be 0.5 to 1.0 times the radius of the cylindrical body from the center.

In addition, a hollow rectifying plate that rectifies the swirling flow by the impeller in the cylinder axis direction is disposed on the downstream side of the impeller, and an air discharge hole is provided at a lower portion of the rectifying plate, and the cylindrical body is surrounded around the rectifying plate. Air supply holes are provided in the wall, and by providing a blower mechanism that supplies air to the inside of the rectifying plate through the air supply holes, air bubbles are discharged into the water through the rectifying plate, and the bubbles pass through the rectifying plate. It can be subdivided by turbulent water flow.
Furthermore, the rectifying plate rectifies the swirling flow by the impeller in the cylinder axis direction, so that the fine bubbles formed on the downstream side of the outer periphery of the impeller and on the upstream side of the rectifying plate are coalesced by the swirling flow and are coarse. Can be prevented.

  In addition, an air chamber is provided around the cylindrical body at the position of the rectifying plate, and a plurality of air supply holes are easily provided around the rectifying plate by communicating the air chamber and the inside of the rectifying plate with the air supply holes. can do.

  Further, by making the cross-sectional shape of the rectifying plate an ellipse or a blade cross-sectional shape, a small vortex can be generated in the water flow that has passed through the rectifying plate, and the bubbles that have passed through this vortex flow can be refined.

  Further, the diameter of the upper part of the cylinder is expanded in a bowl shape, and a disk is provided at a predetermined interval so as to face the enlarged diameter part, so that water flows in from the periphery in the radial inward direction of the cylinder. By providing the inlet, the water flow from the inlet gradually raises the water flow, and the downward flow from the cylinder by the impeller is turned outward at the bottom of the water tank, and the outward flow is directed upward at the side wall of the water tank The upward flow can be made to flow into the cylindrical body as a substantially horizontal inward flow near the water surface, whereby water containing fine bubbles can be circulated throughout the water tank with low power.

It is sectional drawing which shows one Example of the aeration stirring apparatus of this invention. The aeration stirring apparatus is shown, (a) is a cross-sectional view taken along line AA in FIG. 1, (b) is a cross-sectional view taken along line BB, and (c) is an enlarged cross-sectional view showing an impeller and a current plate. The aeration stirring apparatus is shown, (a) is a perspective view showing a cylinder and an air chamber, (b) is a perspective view showing a rectifying plate and a cylinder, and (c) is a cross-sectional view showing an operation of the rectifying plate. It is sectional drawing which shows the conventional aeration stirring apparatus.

  Hereinafter, embodiments of the aeration and stirring apparatus of the present invention will be described with reference to the drawings.

1 to 3 show an embodiment of the aeration stirrer of the present invention.
In this aeration and agitation device, a cylindrical cylinder 4 is arranged around an agitation shaft 3 attached with an impeller 2 that is rotated by an electric motor 1, and a downward flow is generated inside the cylinder 4 by the impeller 2. Yes.
And this aeration stirring apparatus provides the air supply part 51a in the wall part of the cylinder 4 around the slightly downstream side of the impeller 2, and air is supplied to the outer peripheral part of the impeller 2 through the air supply hole 51 of the air supply part 51a. A supply blower mechanism 6 is provided.

  The cylindrical body 4 has its upper portion enlarged in a bowl shape, and a circular plate 42 is horizontally disposed at a predetermined interval so as to face the enlarged diameter portion 41. An inflow port 43 through which water flows is provided.

The diameter (inner diameter) of the enlarged diameter portion 41 of the cylindrical body 4 is 2.5 times or more than the inner diameter of the straight pipe portion of the cylindrical body 4, with a gap about 1/4 of the impeller diameter on the upper side. A disc 42 having an outer diameter similar to the inner diameter of the portion 41 is provided.
As a result, the downward flow from the cylindrical body 4 by the impeller 2 is turned outward at the bottom of the water tank, the outward flow is made upward at the side wall of the water tank, and the upward flow is made to be substantially horizontal in the vicinity of the water surface. It can be made to flow into the cylinder 4 as a counter flow, whereby water containing fine bubbles can be circulated in the entire water tank with low power.

On the downstream side of the impeller 2, a hollow rectifying plate 7 that rectifies the swirling flow generated by the impeller 2 in the cylinder axis direction is disposed. An air discharge hole 71 is provided at the lower part of the current plate 7 having a cross shape in plan view.
An air supply hole 52 is provided in the wall portion of the cylindrical body 4 around the rectifying plate 7, and air is supplied to the inside of the rectifying plate 7 through the air supply hole 52 by the blower mechanism 6. ing.
As shown in FIG. 3C, the rectifying plate 7 has an elliptical or blade cross-sectional shape, and a small vortex is generated downstream of the rectifying plate 7 in the water flow that has passed through the rectifying plate 7. Can be made.

The blower mechanism 6 introduces air into the water from a blower 61 installed on the ground via an air conduit 62.
The blower mechanism 6 is provided with air chambers 63 around the cylinder 4 at the positions of the impeller 2 and the rectifying plate 7, and a plurality of air chambers 63 on the impeller 2 side and the inside of the cylinder 4 are arranged on the circumference. These air supply holes 51 communicate with each other, and the air chamber 63 on the rectifying plate 7 side and the inside of the rectifying plate 7 are communicated with each other through a plurality of air supply holes 52 at joint portions of the rectifying plate 7.

The air supply holes 51 and the discharge holes 71 on the impeller side are circular, and the pore diameter is increased. Specifically, the pore diameter is 3 to 7 mm, preferably about 5 mm or more.
Further, the lower limit position of the air supply hole 51 is a height (water depth) that is lower than the height (water depth) of the lowermost portion of the outer periphery of the impeller 2 by 0.1 to 1 time the impeller diameter. ).

By the way, normally, when the air supply hole 51 or the discharge hole 71 is enlarged, the diameter of the bubble generated in the vicinity of the air supply hole 51 or the discharge hole 71 is also increased, so that the surface area of the bubble per air flow rate, that is, the total surface area per the total volume of the bubble (bubble and The area of the boundary of water) becomes small, and the oxygen dissolution rate in water becomes small.
In addition, since bubbles with a large diameter have a large buoyancy, the bubbles tend to be almost upward even when the direction of the water flow is other than upward, that is, downward or sideways (horizontal direction).
As an example, in order to maintain the residence time of such bubbles, the technology for setting the bubble generation position at the bottom of the tank has been around for a long time, but even in this case, the bubble retention distance is at most a depth of water and is generated. The time from the release to the atmosphere (residence time) is short, and the problem remains that the ratio of the dissolved oxygen amount to the supplied air amount is small (about 20%).

Therefore, in this embodiment, as a means for performing high-efficiency aeration, the bubbles are refined and the bubbles are retained in water for a long time.
The bubble miniaturization and the long-term retention of bubbles will be described below.

As for the bubble miniaturization, it is desirable to make the bubble diameter 1 mm or less, preferably 0.5 mm or less.
As described above, air is discharged from the large-diameter air supply holes 51, and immediately after the discharge, the bubbles are immediately refined into bubbles having a size of 1 mm or less. To pass through a strong location).
As described above, the bubble miniaturization phenomenon occurs remarkably where the water flow velocity gradient is large, but there are two places where the water flow velocity gradient is large in the aeration stirrer of this embodiment.

In the structure of the aeration stirrer of the present embodiment, first, the velocity gradient of the water flow is large in the outer peripheral portion of the impeller 2. Therefore, an air supply hole 51 is provided in the vicinity of the outer peripheral portion of the impeller 2.
The velocity gradient at the outer periphery of the impeller 2 will be described below.
The speed (circumferential speed) of the outer peripheral end of the impeller 2 is determined by the rotational speed and diameter of the impeller 2. As an example, when the rotation speed of the impeller 2 is set to 1000 rpm to 1200 rpm and the diameter is set to 0.2 to 0.3 m, the speed of the outer periphery of the impeller is about 10 to 15 m / s (hereinafter, the average value is 12.5 m / s) ).
At this time, since a water flow having substantially the same flow velocity as that of the impeller 2 is generated on the surface of the outer peripheral portion of the impeller 2, the speed of the water flow is 12.5 m / s in the outer peripheral portion of the impeller 2.
Immediately after the impeller 2, a water flow with a large velocity gradient is generated in the same manner. Therefore, when bubbles are introduced into this water flow, even if the air supply holes 51 of the bubble generation part are as large as 3 to 7 mm, the bubble diameter is In the vicinity of the generating part, it is refined to 1 mm or less by the water flow.

The air supply hole 51 that is the outlet of the bubble is at least 5 mm inside from the inner wall of the cylindrical body wall and outside the cylindrical radius of the cylindrical body by 0.5 times from the center, and the height (water depth) of the outer peripheral portion of the impeller 2 The air chamber 63 is provided on the downstream side by a length of 0.1 to 1 times the impeller diameter, and the air chamber 63 is provided around the cylindrical body 4 where the air supply portion 51a is located. Air is supplied at 61 through an air conduit 62.
Since the air supply hole 51 or the discharge hole 71 has a shallow water depth, the power of the blower 61 for blowing air can be small.

Next, as a place where the velocity gradient of the water flow is large, there is a lower side of the rectifying plate 7 as a place where the absolute value of the water flow velocity is high (2 m / s or more) other than the above. Is big.
In the aeration stirrer of the present embodiment, the lower side (downstream side) of the rectifying plate 7 for suppressing the horizontal swirling flow has a large velocity gradient of the water flow and a fine vortex is generated. An air discharge hole 71 is provided in the lower portion of the air flow passage, and the air is supplied by a blower 61 to the inside of the rectifying plate 7 which is hollow.

Next, the extension of the residence time in the bubble tank will be described.
As a means for retaining the micronized bubbles in the tank for a long time, it is made to flow along with a water flow that stays for a long time, that is, a water flow that draws a long trajectory.
The water flow is such that it occurs at the surface layer part and goes from the surface layer part to the bottom of the water tank, and at the bottom part goes to the outer peripheral part and rises near the wall surface. Therefore, on average, the water tank stays for a long time.
The position where the bubbles for flowing along with the water flow are generated, that is, the position of the air supply hole 51 or the discharge hole 71 is a surface layer portion when viewed macroscopically.
By doing so, the bubbles pass through a staying distance of at least twice the length of the water depth, at least in the wind of air release from the surface layer to the bottom of the water tank and from the bottom to the surface.
In addition, the bubbles flow in various traces along with the water flow, and some of them repeat the circulation many times, such as going from the surface layer to the bottom, from the bottom to the surface water intake without going to the surface, and flowing downward again. Yes, the average residence time of all bubbles is lengthened.

  Further, in the conventional aeration and stirring device, when air is sent to the bottom of the water tank, a high pressure is required, and there is a problem that the required power of the blower 61 is large, but in this embodiment, air is supplied at the surface layer of the water tank. Since the blow-in structure requires only a small blower power, and the air supply hole 51 can be enlarged, the resistance of the bubble outlet portion is reduced and the required power of the blower 61 can be suppressed.

Thus, the aeration stirrer of the present embodiment can obtain the following effects by the above structure.
1. The fine bubbles produced by the aeration and agitation apparatus of the present embodiment have a larger surface area and larger contact area with water than coarse bubbles of the same volume, so that the oxygen dissolution rate is increased.

2. Since the fine bubbles having a diameter of about 0.05 mm to 0.5 mm have a small buoyancy, almost the entire bubble flows together with the water flow, and therefore stays in the water for a long time by flowing along with the circulating water flow.
Due to this effect, an average of 40% or more of the oxygen in the bubbles dissolves in water before being released to the atmosphere.

3. An air supply hole 51 or a discharge hole 71 can be provided at a shallow depth (water depth of about 1 m, or about 10% for a deep tank), and air can be fed into the water from the air supply hole 51 or the discharge hole 71. Therefore, the influence of the water pressure is small, so that the required power of the blower 61 can be smaller than that of the conventional underwater aeration type in which the blower 61 is blown into a position having a water depth of about 5 m.
Looking only at the water pressure as the operating condition, it becomes extremely small, about 1/5 of the conventional machine and about 1/10 in the deep tank.

4). Since the diameter of the air supply hole 51 or the discharge hole 71 can be increased to 3 mm to 7 mm, there is an effect that clogging is difficult. In addition, the air discharge resistance is small, and the blower power can be reduced.

5. The upper portion of the cylindrical body 4 is enlarged in a bowl shape, and a circular plate 42 is horizontally disposed at a predetermined interval so as to face the enlarged diameter portion 41. By providing the inflow port 43 for inflowing water, the inflowing water accelerates in the flow passage where the flow passage area gradually decreases in the same manner as when flowing in the gentle reduction pipe, so there is little loss and a large flow rate with low power. Therefore, the bubbles and water can be circulated throughout the water tank with low power.

6). With the following configuration, the refined bubbles of 0.5 mm or less are prevented from being coarsened again by coalescence, and the fine bubbles spread as they are throughout the tank.
Due to the rotation of the impeller 2, the water flow on the downstream side of the impeller 2 becomes a spiral flow including a speed component swirling around the stirring shaft 3.
The water flow on the downstream side of the impeller 2 flows in the axial direction because the swirl component is suppressed by the rectifying plate 7 as shown in FIG. Therefore, it is possible to prevent bubbles from being collected at the center of rotation and coalesced by the centrifugal force generated by the swirling flow.

7). Since the cross-section of the rectifying plate 7 is elliptical or wing-shaped, the water flow that has passed through the rectifying plate 7 has a small vortex on the downstream side, but the bubbles generated at this location are refined by the water flow.

  As mentioned above, although the aeration stirring apparatus of this invention was demonstrated based on the Example, this invention is not limited to the structure described in the said Example, The structure is suitably changed in the range which does not deviate from the meaning. can do.

  The aeration stirrer of the present invention is characterized by performing aeration operation for dissolving oxygen in water with high efficiency, ensuring a sufficient oxygen dissolution rate for dissolving oxygen with respect to the amount of water, and preventing clogging of the air supply holes. Therefore, it can be suitably used for an aeration stirrer for sewage treatment, and can also be used for, for example, a dyeing or food aeration stirrer.

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Impeller 3 Stirring shaft 4 Cylindrical body 41 Expanded part 42 Disc 43 Inlet 51 Air supply hole 51a Air supply part 52 Air supply hole 6 Blower mechanism 61 Blower 62 Conduit 63 Air chamber 7 Rectifying plate 71 Exhaust hole

Claims (6)

  In an aeration stirrer in which a cylindrical body is arranged around a stirring shaft to which an impeller is attached, and a downward flow is generated inside the cylindrical body by the impeller, an air supply hole is formed in a wall portion of the cylindrical body around the impeller. An aeration stirrer provided with a blower mechanism that supplies air to the outer peripheral portion of the impeller through the air supply hole.   The aeration stirrer according to claim 1, wherein an air chamber is provided around the cylinder at a position downstream of the impeller, and the air chamber and the inside of the cylinder are communicated with each other through an air supply hole.   On the downstream side of the impeller, a hollow rectifying plate that rectifies the swirling flow by the impeller in the cylinder axis direction is provided, and an air discharge hole is provided at the lower portion of the rectifying plate, and the wall of the cylindrical body around the rectifying plate The aeration and agitation device according to claim 1 or 2, further comprising a blower mechanism that is provided with an air supply hole and supplies air into the rectifying plate through the air supply hole.   The aeration stirrer according to claim 3, wherein an air chamber is provided around the cylindrical body at the position of the rectifying plate, and the air chamber and the inside of the rectifying plate are communicated with each other through an air supply hole.   The aeration stirrer according to claim 3 or 4, wherein a cross-sectional shape of the rectifying plate is an ellipse or a blade cross-sectional shape.   The upper part of the cylindrical body is expanded in a bowl shape, a disk is arranged at a predetermined interval so as to face the expanded diameter part, and an inflow port through which water flows in from the periphery inward in the radial direction of the cylindrical body The aeration stirrer according to claim 1, wherein the aeration stirrer is provided.

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