JP5579562B2 - Aeration stirrer - Google Patents

Description

  The present invention relates to an aeration stirrer, and in particular, easily switches between an aerobic operation (aeration operation) for supplying air (oxygen) into water and an anaerobic operation (agitation operation) without supplying air (oxygen) into water. In particular, the present invention relates to an aeration stirrer capable of energy efficient aerobic operation.

Conventionally, a screw type aerator as shown in FIG. 3 has been put to practical use as an aerator used in a sewage treatment plant such as sewage (see Patent Document 1).
The screw type aerator includes an electric motor 30, a hollow shaft 1 rotated by the electric motor 30, an electric valve 40 attached to the upper end of the hollow shaft 1, and a blade 20 spirally on the outer peripheral surface of the lower end portion of the hollow shaft 1. The screw 2 is configured by attaching the pipe 2, the pipe-shaped cover 52 covering the outer periphery of the hollow shaft 1, and the eddy current preventing plate 51 attached to the lower end of the cover 52.

  In this screw type aerator, when the screw 30 is rotated through the hollow shaft 1 by driving the electric motor 30, a negative pressure is generated in the tip water region of the screw 2 due to the water flow generated thereby. Due to this negative pressure, when the electric valve 40 is opened, air is sucked through the electric valve 40, and the sucked air is discharged into the water through the hollow shaft 1. At this time, the air discharged into the water is refined by the action of the blades 20 of the screw 2 and the water flow, and is sent to the water deeply along the water flow. (Aerobic driving). Further, when the electric valve 40 is closed, air is not sucked, and the sewage in the aeration tank is stirred by the water flow generated by the rotation of the screw 2 (anaerobic operation).

JP-A-4-277089

By the way, since the conventional screw type aerator is a system in which air is self-supplied by the negative pressure generated in the tip water region of the screw 2, the vertical distance from the water surface to the tip of the screw 2, that is, the immersion depth is about 0. It was necessary to keep it at about 3 m.
The reason is that (1) if the immersion depth is made too shallow, the rotating screw 2 will not be able to generate a good water flow by approaching the water surface. Conversely, (2) the immersion depth is made too deep. Since the water pressure (static pressure) in the region of the tip of the rotating screw 2 increases, the negative pressure effect due to the rotation of the screw 2 is diminished, and the amount of air to be self-supplied is reduced. Not only was it not possible to drive, but also the necessary amount of air could not be sent into the water.

  As described above, in the conventional screw type aerator, it is necessary to keep the immersion depth at about 0.3 m, and it is necessary to rotate the screw at a constant speed suitable for water flow generation. Adjustment to reduce the amount of air, such as closing the electric valve 40 half, was possible, but adjustment to increase the amount of air was not possible.

And it is difficult for the reason of said (2) to extend the residence time until the bubble emitted from the front-end | tip part of the screw 2 arrives at the water surface, and to increase the immersion depth in order to raise the efficiency of oxygen transfer speed. Met.
In addition, since the structure is such that the amount of air cannot be increased, there has been a limit to improving energy efficiency.

  The present invention goes beyond the limitations of conventional screw aerators to increase the immersion depth, increase the amount of air, and suppress the increase in power accordingly. It aims at supplying the aeration stirrer which can perform an aerobic operation with high efficiency.

In order to achieve the above object, the aeration stirrer of the present invention is an aeration stirrer provided with a screw at the lower end of a hollow shaft that is driven to rotate by an electric motor, in the cover provided on the outer peripheral portion of the hollow shaft, An air chamber is formed inside as a sealed structure except for a lower end portion that penetrates the hollow shaft and is immersed in water, and two opening holes are formed in the upper portion of the hollow shaft with a space in the axial direction of the hollow shaft. And the inside of the hollow shaft and the air chamber communicate with each other through the opening hole, and air is forcibly sent from the air supply source to the air chamber through the air conduit during the aerobic operation. During the anaerobic operation, the electric valve provided in the air conduit is closed, and the water that has risen inside the cover is sucked into the inner side of the hollow shaft from the lower opening hole .

  In this case, the aeration stirrer according to claim 1, wherein a blower is used as an air supply source.

  Further, the hollow shaft can be rotationally driven by an electric motor having a solid shaft.

  According to the aeration stirrer of the present invention, the inside of the cover provided on the outer peripheral portion of the hollow shaft penetrates the hollow shaft and forms an air chamber inside as a sealed structure except for a lower end portion immersed in water. An opening hole is formed in the upper part of the shaft so that the inside of the hollow shaft communicates with the air chamber through the opening hole, and the air chamber is connected to the air chamber from the air supply source through an air conduit during aerobic operation. By forcibly sending air, the pressure of the air forced into the air chamber assists the negative pressure due to the rotation of the screw, increasing the screw immersion depth or increasing the amount of air. In addition, by suppressing the increase in power corresponding thereto, it is possible to perform an aerobic operation with high energy efficiency as a result.

By forming a plurality of opening holes at intervals in the axial direction of the hollow shaft, water rises between the hollow shaft and the cover during anaerobic operation, reaches the vicinity of the motor, and the opening hole rises. It is possible to prevent the waste contained in the water from being clogged by drying, and by providing an electric valve in the air conduit, an aerobic operation and an anaerobic operation performed by closing the electric valve are performed. It can be switched easily.

  Further, by using a blower as the air supply source, the air supply source can be configured by a simple mechanism.

  Moreover, a general-purpose electric motor can be used by rotationally driving the hollow shaft with an electric motor having a solid shaft.

It is explanatory drawing which shows one Example of the aeration stirrer of this invention, (a) is a top view, (b) is a front view. It is explanatory drawing which shows the water flow image of the hollow shaft vicinity at the time of the anaerobic operation of the aeration stirrer. It is explanatory drawing which shows the conventional aeration stirrer.

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

1 to 2 show an embodiment of the aeration stirrer of the present invention.
This aeration stirrer relates to an aeration stirrer in which a screw 2 is provided at the lower end of a hollow shaft 1 that is driven to rotate by an electric motor 3 as in the conventional aeration stirrer described in FIG.

  And this aeration stirrer forms the air chamber 50 inside as a sealed structure except the lower end part 5a which the hollow shaft 1 penetrates the inside of the cover 5 provided in the outer peripheral part of the hollow shaft 1, and is immersed in water. Open holes 1a and 1b are formed in the upper part of the hollow shaft 1 so that the interior of the hollow shaft 1 and the air chamber 50 communicate with each other through the open holes 1a and 1b. Air is forcibly sent from the supply source 6 to the air chamber 50 through the air conduit 4.

In this case, a blower can be used as the air supply source 6 which is a means for forcibly sending air into the air chamber 50 via the air conduit 4.
Thereby, an air supply source can be comprised by a simple mechanism.

Further, as the electric motor 3, an electric motor having a solid shaft is used.
Thereby, a general purpose electric motor can be used and repair etc. can be performed easily.

In addition, an electric valve 4 a is provided in the air conduit 4.
This facilitates an aerobic operation performed by opening the electric valve 4a and forcibly sending air from the air supply source 6 to the air chamber 50 via the air conduit 4 and an anaerobic operation performed by closing the electric valve 4a. You can switch to

By the way, in the anaerobic operation performed by closing the electric valve 4a, water rises between the hollow shaft 1 and the cover 5, reaches the vicinity of the electric motor 3, and the inside of the cover 5 is contaminated and contained in the rising water. There was a problem that the garbage was blocked by drying.
The mechanism is that in anaerobic operation, the inside of the cover 5 becomes negative due to the negative pressure at the tip of the screw 2, and water rises between the hollow shaft 1 and the cover 5. The water level rises to the connection part of the hollow shaft 1.
At this time, the negative pressure at the tip of the hollow shaft 1, is about 2.5mH ₂ 0~4.0mH ₂ 0 by actual measurement.
In order to prevent this, in this aeration stirrer, a plurality of opening holes 1a and 1b are formed at intervals in the axial direction of the hollow shaft 1 (here, the opening hole 1b is located at a position slightly above the water surface). To be formed.)
Thereby, the water that has risen inside the cover 5 during the anaerobic operation is sucked into the hollow shaft 1 from the opening hole 1b, and as a result, even if the water rises between the hollow shaft 1 and the cover 5, Water does not rise to the upper opening hole 1a or the connection portion between the output shaft of the electric motor 3 and the hollow shaft 1, and in particular, dust contained in the water from which the opening hole 1a has risen is blocked by drying. Can be prevented.

Next, the operation of this aeration stirrer will be described.
First, for comparison, when the conventional aeration stirrer described in FIG. 3 is driven at a required power of 3.7 kW with an installation angle of 45 degrees and an immersion depth of the tip of the screw 2 of 0.3 m, it is appropriate. A water flow of 2.4 m ³ / min was able to be released into the water by self-sufficiency. When the value obtained by dividing the air flow rate Qa at this time by the required power P is defined as the air input efficiency η _air ,
η _air = Qa / P = 2.4 / 3.7 = 0.65 m ³ / (min · kW)
It becomes.
If the immersion depth at the tip of the screw 2 is changed from 0.3 m to 0.7 m in order to allow bubbles to reach deeper in the water tank, the amount of air due to self-sufficiency decreases to 1.1 m ³ / min. .
Therefore, in addition to self-sufficiency, air is forcibly fed into the air chamber 50 from the blower as the air supply source 6 through the air conduit 4. At this time, the air pressure by the blower as the air supply source 6 is 0.4 mH ₂ O. This value is small for the deep water depth, and the required power of the blower is 0.44 kW.
Here, the required power of the blower 0.44 kW is calculated based on the following calculation formula.
Thermal insulation head: H _ad = {κ / (κ-1)} · R _gas · T1 · {(P2 / P1) ^{(κ-1) / κ-} 1} = 330 (mm)
κ: Specific heat ratio 1.4
R _gas : Gas constant (kgm / kgK) 29.5
T1: Inlet temperature (total temperature) K 293.2
P1: Inlet total pressure (kg / m ² abs) 10330
P2: outlet total pressure (kg / m ² abs) 10330 + 400 (increase in static pressure)
Air volume Q = 2.4m ³ / min
Weight flow rate G = 1.2 × Q / 60 = 0.054 kg / s
Air power P = G × Had / 102 = 0.174kW
Blower efficiency η _b = 0.40 Blower required power L = P / η _b = 0.44 kW
By adding a 0.44 kW blower to the 3.7 kW aeration stirrer, the amount of air can be maintained at 2.4 m ³ / min even if the immersion depth is 300 mm.
The amount of air was 2.7 m ³ / min, which was larger than that in actual measurement. At this time, the air charging efficiency η _air is
η _air = Qa / P = 2.7 / (3.7 + 0.44) = 0.66 m ³ / (min · kW)
Thus, the immersion depth is almost the same as when the self-sufficiency is 300 mm.

Here, the air input efficiency η _air described so far is a measure of the aeration efficiency, but it is not itself. In the first place, the aeration efficiency is a value per power of the rate at which oxygen in the air dissolves in water, that is, the oxygen dissolution power efficiency Ep, which is difficult to obtain by simple calculation and is obtained by actual measurement.

As shown in Table 1, it has been confirmed by measurement that the oxygen dissolution power efficiency Ep increases by several percent.
This result is considered to be due to the phenomenon that the aeration time (oxygen dissolution power efficiency Ep) is improved by increasing the immersion depth and extending the residence time of bubbles.

Next, the effect that the energy efficiency of stirring can be maintained by this aeration stirrer will be described.
First, when the immersion depth at the tip of the screw 2 is increased and the bubbles are introduced into a deep position, the flow rate of the horizontally flowing water is reduced due to the increased tendency of the gas and liquid to flow vertically upward together. As a result, there is a concern that the stirring efficiency may be reduced as a secondary effect, but on the other hand, there is the following effect of increasing the stirring efficiency, and it has been confirmed through experiments that the energy efficiency of stirring can be maintained by offsetting them. ing.
Regarding the generation of water flow, that is, stirring, first, considering the flow rate of water in the vertical direction, the decrease in the bottom of the water flow is suppressed by shortening the distance from the water flow generation position to the bottom by increasing the immersion depth. On the other hand, the position where the water flow is generated horizontally and horizontally is shifted downward by 0.4 m, so that, for example, in the cross section of the water channel formed from the water depth of the water tank of 2 m or more and the water channel width, the water flow generation position is more central. The effect of sliding is obtained.
As a result of confirming the above contents by experiments using an endless water channel having a water depth of 2.5 m, a water channel width of 2.0 m, and a water channel length of 20 m or more, there is almost no difference in the bottom part flow velocity, and the energy efficiency of stirring can be maintained. The effect was confirmed.
Specifically, the average flow rate was 28.7 cm / s at an immersion depth of 0.3 m, whereas the average flow rate was 26.3 cm / s at an immersion depth of 0.7 m.

And according to this aeration stirrer, as mentioned above, the opening holes 1a and 1b are formed in the upper part of the hollow shaft 1 of the aeration stirrer, and the outer peripheral portion thereof is the air chamber 50 surrounded by the cover 5, The air chamber 50 can be additionally supplied with air by the air supply source 6 provided on the ground side via the air conduit 4. However, the energy efficiency is controlled by controlling the rotation speed of the air supply source according to the required amount of dissolved oxygen. A good aerobic driving becomes possible.
The control of the air supply amount can also be adjusted by adjusting the opening degree of the electric valve 4 a provided in the middle of the air conduit 4. Moreover, by using them together, it is possible to suppress the reduction in efficiency at the time of the low rotation speed of the air supply device, which is often found in the air supply device.

  As described above, the aeration stirrer of the present invention has been described based on the examples thereof, but the present invention is not limited to the configurations described in the above examples, and the configurations described in the respective examples are appropriately combined, etc. The configuration can be changed as appropriate without departing from the spirit of the invention.

  The aeration stirrer of the present invention can perform aerobic operation with high energy efficiency as a result of increasing the immersion depth, increasing the amount of air, and further suppressing the increase in power accordingly. Since it can do, it can use suitably for the use of an aeration stirrer.

DESCRIPTION OF SYMBOLS 1 Hollow shaft 2 Screw 3 Electric motor 4 Air conduit | pipe 4a Electric valve 5 Cover 50 Air chamber 6 Air supply source

Claims (3)

In the aeration stirrer provided with a screw at the lower end of the hollow shaft that is driven to rotate by an electric motor, the hollow shaft penetrates the cover provided at the outer peripheral portion of the hollow shaft and excludes the lower end that is immersed in water. As an airtight structure, an air chamber is formed inside, and two opening holes are formed in the upper part of the hollow shaft with an interval in the axial direction of the hollow shaft. In the aerobic operation, air is forcibly sent from the air supply source to the air chamber through the air conduit, and in the anaerobic operation, the electric valve provided in the air conduit is closed. An aeration stirrer characterized in that water that has risen inside the cover is sucked into the hollow shaft from the lower opening hole .   The aeration stirrer according to claim 1, wherein a blower is used as an air supply source. Aeration agitator according to claim 1 or 2, wherein it has to rotate the drive hollow shaft by an electric motor having a solid shaft.

Images