JPS586290A - Aeration device - Google Patents

Abstract

PURPOSE:To form gas-liquid circulation flow over the entire part of an aeration tank by forming a suction port in the upper part of a casing installed in the bottom part, an impeller at the intermediate and a discharge flow passage which is roughly horizontal and directs toward the outer side in a radial direction in the lower part. CONSTITUTION:When a motor 1 is run, an impeller 2 mounted in the end part of a motor shaft 1 revolves, and the treating liquid in an aeration tank is sucked through a suction port 10 as shown by an arrow D and is discharged in a horizontal direction through a discharge port 8 near the bottom part 9 of the aeration tank. At this time, oxygen or air is supplied through the opening 3a of an air diffusion pipe 3 and therefore the treating liquid is mixed and agitated with the oxygen or air to form air-liquid mixed phase flow. This air-liquid mixed phase flow is flowed out in parallel from the neighborhood of the part 9 of the aeration tank. The sharp decrease in the velosity of the discharge flow is obviated by the reaction of moving this as entraining flow and the overall decrease in the velocity of flow is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aeration device for purifying wastewater in a sewage treatment plant such as a factory wastewater treatment plant or a city sewage treatment plant.

Traditionally, sewage treatment methods include liquid surface agitation type, aeration tube type,
Although techniques such as the aeration plate type are known, recently mechanical aeration devices such as aerators with impellers have been used to forcefully generate a gas-liquid circulation flow within the aeration tank, thereby increasing aeration efficiency. technology is being adopted.

An example of such prior art is shown in FIG. 1, in which an impeller 2' rotated by a motor 1- is housed in a casing 3', and the liquid flows as indicated by arrow A. It is designed to flow from the bottom to the top or diagonally upward. Then, air is sucked in through the air supply pipe 4 to effect aeration.

Furthermore, the conventional example shown in FIG. 2 is of a type in which the liquid is suspended on the liquid surface by a float 5', and an impeller 7' rotated by a motor 6' moves the liquid into the casing 9' indicated by the arrow B.
As shown, the air is sent from above to below, and during this time air is sucked in from the supply pipe 8 to effect aeration.

Although such conventional devices are effective in themselves, they do not circulate the gas-liquid multiphase flow to the corners of the aeration tank.
In order to improve the aeration performance, a relatively high discharge flow rate is required, and it is also necessary to prevent the discharge flow from decelerating as much as possible even after discharge. If anything,
This is because the gas-liquid multiphase flow usually rises to the water surface without reaching the wall surface of the aeration tank, and mixing and agitation within the tank is not performed sufficiently. Furthermore, if the flow velocity at the bottom was low, activated sludge would settle, causing a problem in that the aeration performance would deteriorate.

Therefore, it is an object of the present invention to provide an aeration device that does not relatively slow down the flow velocity after discharge and can thereby generate a gas-liquid circulating flow throughout the aeration tank.

According to the invention, the aeration device is installed at the bottom of the aeration tank,
The discharge port for the gas-liquid multiphase flow opens substantially in the horizontal direction. Therefore, the gas-liquid multiphase flow flows horizontally near the bottom of the aeration tank, and then rises along the side wall of the aeration tank,
After flowing near the liquid level, it flows into the aeration device again, and substantially the entire inside of the aeration tank is mixed and stirred.

The present invention will be described in detail below with reference to FIG. The aeration device implementing the present invention, which is designated as C as a whole, is located at the bottom 9 of the aeration tank.
It is installed on the top and consists of a base 11 located on the bottom 9, a casing 7 formed on the base 11, and a motor 1 installed above the casing 7. The casing 7 has a suction port 10 at its upper end,
Inside the intermediate portion, a slant wheel 2 rotated by a motor 1 is provided in a known manner. For example, an underwater geared motor is used as the motor 1. It is supported by a support 6 from the casing 7.

Therefore, in the illustrated embodiment, the casing 7 is formed into a cylindrical shape with an upwardly widening portion above the impeller 2, and a pump unit equipped with a motor and an impeller is provided at the axis or central portion of the casing 7. The discharge passage 12 formed in the lower part of the casing 7 is formed by an outer plate 13 extending downward and an inner plate 1'4 provided on the radially inner side of the outer plate 13 and also extending downward. is,
The discharge flow flowing downward from the impeller 2 is gently bent horizontally by the inner and outer plates 13 and 14, and is then discharged horizontally and radially outward from the ring-shaped discharge port 8. It looks like this.

According to a preferred embodiment of the present invention, if the distance from the bottom 9 of the aeration tank to the lower end 8' of the outlet 8 is a, and the height or vertical width of the outlet 8 is b, then ratio a
/b is formed to be 3.0 or less.

On the other hand, a ring-shaped air supply pipe 4 is provided on the outer periphery of the casing 7, and an air supply port 5 is formed in this air supply pipe 4, and is connected to an external supply source such as oxygen or air via a pipe (not shown). ing. A plurality of air diffusers 3 extend from the air supply pipe 4 into the discharge flow path 12, and these air diffusers 3 constitute a stay of the ring-shaped air supply pipe 4. The diffuser pipe 3 has a plurality of openings 3a in order to diffuse oxygen, air, etc. at the exposed flow path 12. In the figure, 15 is an underwater cable for power, 16 is an underwater cable for various protection devices, and 17 is a chain for suspending the aeration system @C. During operation, when the motor 1 is rotated,
The impeller 2 is attached to the end of the motor shaft 1a and rotates,
The processing liquid in the aeration tank is sucked in from the suction port 10 as shown by the arrow, and is discharged horizontally from the discharge port 8 near the bottom 9 of the aeration tank.

At this time, since oxygen or air is supplied from the opening 3a of the aeration tube 3, the processing liquid is mixed and stirred with the oxygen or air, resulting in a gas-liquid multiphase flow.

This gas-liquid multiphase flow flows out from near the bottom 9 of the aeration tank horizontally, that is, parallel to the bottom 9. In the conventional example shown in Figs. 1 and 2, the discharge flow moves the still water on both sides above and below it as an accompanying flow, and the flow velocity decreases rapidly, but in this example, at least there is no still water on the lower side of the discharge flow. , or because it is small, the flow velocity does not suddenly decrease as a reaction to moving this as an entrained flow, and overall the flow velocity does not need to decrease as much.

FIG. 4 is a diagram showing the effect of the present invention, in which the discharge flow from the aeration device C installed near the bottom of the aeration tank E first flows outward in the radial direction along the bottom 9, as shown by the arrow F. The flow then flows upwardly along the side wall 18, horizontally radially inwardly again near the liquid level S, and downwardly above the aerator C.

Therefore, according to the present invention, the discharged gas-liquid multiphase flow flows to every corner of the entire l-air tank E, so that the aeration performance is improved.

Furthermore, since the flow velocity at the bottom 9 can be kept high, there is no sedimentation of activated sludge, further improving efficiency.

When carrying out the present invention, the bottom of the aeration tank may be partially raised or lowered, and in that case, the portion of the aeration tank with the largest plane area is defined as the bottom. FIG. 5 shows a case where a part 9a of the bottom part 9 of the aeration tank is lowered, and in this case, a leg part 20 is provided and the aeration device C is mounted on the leg part 20.
, and the position of the discharge port 8 is a as explained in Fig. 3.
/b should be 3°0 or less. In addition, if a part is elevated, it may be installed at the bottom 9.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a partial cross section of an example of a conventional aeration device, FIG. 2 is a schematic cross-sectional side view showing another example of a conventional aeration device, and FIG. 3 is a side view showing an example of an embodiment of the present invention. FIG. 4 is a side view showing the effects of the present invention, and FIG. 5 is a side view showing an example of installing an aeration device implementing the present invention in an aeration tank. 1... Motor 2... Impeller 3
... Air diffuser pipe 4 ... Air supply pipe 7.
...Casing 8...Discharge port
9... Bottom 10... Suction port 12.
...Discharge channel patent applicant Ebara Corporation Ebara Infilco Corporation

Claims (2)

[Claims] (1) Equipped with a casing installed at the bottom of the aeration tank,
The casing has an inlet in the upper part, an impeller in the middle, and a discharge passage in the lower part, and the outlet of the discharge passage is substantially horizontal and faces radially outward; An aeration device characterized in that the aeration device is located near the bottom of the aeration tank. (2) The distance between the lower end of the discharge port and the bottom of the aeration tank is a, the vertical width of the discharge port is b, and the ratio a/b is 3.0.
An aeration device according to claim 1, which is as follows.