JPS588588A - Aerator - Google Patents

Abstract

PURPOSE:To increase aeration amount, by a method wherein the passage from an impeller to a discharge port is constructed in the form of an umbrella-shaped nozzle, and a gas diffusing port is located at a position in the region wherein the angle included between the meridional streamline drawn from the impeller to the discharge port and a horizontal line is not larger than 60 deg.. CONSTITUTION:The passage from the impeller 3 to the discharge port 10 is constructed in the form of an umbrella-shaped nozzle, and the gas diffusing port 6 for supplying a gas into the liquid to be treated is located at a position in the region wherein the angle theta included between the meridional streamline A-A drawn from impeller 3 to the port 10 and the horizontal line B-B is not larger than 60 deg., and the ratio of L/H satisfies the condition of 0.5<=L/H<=2.5, where L is the distance from the port 6 to the port 10 measured along the meridional streamline and H is the height of the vane of the impeller 3. Accordingly, a gas- liquid mixed flow is passed at a bottom part of an aeration tank, so that the depth of the liquid being treated can be utilized effectively and the aeration performance can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aeration device used for purifying wastewater.

Conventionally, in sewage treatment plants such as factory wastewater treatment plants and urban sewage treatment plants, the liquid surface agitation type, aeration tube type, and a number of diffuser plate methods have been generally used, but recently, methods with improved aeration efficiency have been used. Aerator-type aeration equipment, such as aerator with an impeller! As a result, Klk decided to adopt a method of forcibly creating a gas-liquid circulation flow in the aeration tank. Most of these impeller-equipped aerators use an impeller installed so that the axis is aligned vertically, and the flow direction inside the impeller is from bottom to top, because it is easy to supply air force in pure oxygen. It was also of a first stop discharge type, with the discharge diagonally upward from the bottom. That is, the supplied air was rounded with an upward floating speed, and the direction of the gas-liquid mixing flow was also upward, which was advantageous in that the other party could increase the amount of gas.

No. 111 shows an example of the conventional top discharge type, in which the impeller 13 rotated once by the submersible motor 12 is #I inside the casing 11.
C), due to one turn of the impeller 13] suction port 15
The processing liquid in the aeration tank is sucked in from the aeration tank, flows diagonally upward from below as shown by the arrow, and is discharged through the discharge port 16). Then, pure oxygen or air is supplied from the air supply pipe 14, mixed and stirred with the processing liquid, and discharged from the discharge port 16 as a gas-liquid mixed flow.

However, aeration performance is closely related to the water depth of the treated solution (mK), and in aeration tanks with the same water depth, the top discharge type does not allow the flow to reach the bottom of the cypress, which is disadvantageous because the water depth is not used effectively. . Another disadvantage is that the flow rate at the bottom of the tank is low, causing activated sludge to settle and drying out. For this reason, in an impeller in which snow is thrown so that the shaft center is vertical, the flow direction inside the impeller is set from top to bottom or diagonally downward from top, so that the gas-liquid mixed flow passes through the bottom of the tank. A lower discharge type was proposed.

Figure 2 shows the proposed lower discharge type aeration device.
A KFi impeller 3 is attached to the shaft end of the submersible guard motor 20, and the impeller 3 is rotated by the submersible guard motor 2, and the treated liquid in the aeration tank is sucked in from the suction 19 and discharged from the discharge port 10. do. An upstream diffuser pipe 51 or 7 or a downstream diffuser pipe 5b is provided close to the impeller 3, and gas such as pure oxygen or air is supplied from the upstream diffuser pipe 5a or the downstream diffuser pipe 5b. The mixture is mixed with the treatment liquid and stirred to form a gas-liquid multiphase flow, which is then discharged from the discharge port IO. The air diffuser pipes 5a, 5'bK are provided with air diffuser holes 6. As shown in the air diffuser pipes 5a and 5bij No. 3r8, the air supply port 8 connected to the air supply pipe 7 is connected to the air supply pipe 7, and the air supply port 8 is connected to the air supply pipe 7.
Connected to a supply source such as air. The submersible geared motor 2 and the casing 1 are connected by a motor support 4).

However, in the above-mentioned bottom discharge type aeration device, as shown in Fig. 3, the position of the gas diffuser port 6 is immediately after the upstream side or downstream side of the impeller 3, and the amount of gas cannot be increased. There was a drawback. In other words, if air is diffused from the upstream side,
When the amount of air diffused is large, the impeller suction side is temporarily blocked by gas, and the impeller 3 becomes unable to pump water, and the gas is not sucked in, and the processing liquid flows back to the suction port 9. In addition, even if air can be diffused immediately after the downstream side of the impeller, when the amount of air diffused is large, the position of the air diffuser 6 is vertically below the impeller 3, so some of the gas will accumulate in the impeller. Eventually, the entire surface becomes gas, and the impeller 3 becomes unable to pump up the water, and the gas is not discharged from the discharge port 10, but the buoyancy of the bubbles causes the processing liquid to flow back to the suction port 9. In either case, a gas-liquid mixed phase circulating flow is not formed, so the aeration performance is significantly reduced.

The present invention has been made for the purpose of solving the above-mentioned drawbacks of the aeration device, eliminating the influence of gas on the impeller, and providing an aeration device that can increase the amount of aeration.

Therefore, in this invention, the impeller axis is set in the vertical direction,
In an aeration device in which the flow direction inside the impeller is from top to bottom or diagonally downward from top, the flow path from the impeller to the discharge port is shaped like an umbrella nozzle, and the aeration port supplies gas into the processing liquid. The location is such that gas buoyancy does not have a significant effect on the flow. That is, it is provided in a range where the angle between the meridional streamline from the impeller to the discharge port and the horizontal line is 60° or less. In addition, in a sealed flow path from the air diffuser to the outlet, the dissolution of oxygen progresses more rapidly than in the free flow after leaving the outlet. It is desirable to keep the distance as much as possible. Although it is not possible to increase the same distance from a manufacturing standpoint, the ratio of the same distance on the meridional streamline to the height H of the impeller blade is set to 0.5≦h≦2.5.

This eliminates the effect of gas on the impeller, making it possible to increase the amount of aeration and ensuring sufficient mixing and agitation of the processing liquid and gas in the umbrella nozzle downstream of the first aeration position. However, the aeration performance is significantly improved.

FIG. 3 shows an embodiment of the present invention, which is substantially the same as that shown in FIG. 2 except for the position of the air diffuser, so the same parts as in FIG. 2 are given the same reference numerals.

The flow path from the impeller 3 to the discharge port 10 has an umbrella-shaped nozzle shape, and the position of the diffuser port 6 for supplying gas into the processing liquid is in the meridian direction from the impeller 3 to the discharge port 10. Menryu 11
The air diffuser port 6 is provided in a range such that the angle θ between A-A (A-A indicates one of the meridional streamlines) and the horizontal line B-H is 60° or less. From the position of the discharge port 10
The ratio d between the distance on the meridional streamline up to the height H of the blade of the impeller 3 (0.5≦Koma■≦2.5).

In this way, the single impeller axis is vertical and the flow direction inside the impeller is from top to bottom or diagonally downward from top to bottom discharge type. This allows effective use of the water depth of the treatment liquid, improving aeration performance. In addition, the bottom discharge type has a part where the flows in the tank intersect as shown in Figure 5, but the bottom discharge type does not have this as shown in Figure 4, so there is less flow velocity reduction due to flow collision, and the tank The internal flow velocity can be maintained high.

Also, if the flow path from the impeller part to the discharge port is shaped like an umbrella-shaped nozzle, and the distance from the aeration port to the discharge port is K O,5Q%≦2.5 as described above, then K. After the gas is supplied, the processing liquid and gas are sufficiently mixed and stirred within the nozzle up to the discharge port without slowing down the flow due to external still water. Furthermore, the flow velocity at the bottom of the tank after being discharged can be increased, eliminating sedimentation of activated sludge and improving aeration performance.

In addition, by using the bottom discharge type, the amount of gas that can be supplied generally decreases, but the position of the diffuser hole of the diffuser pipe can be adjusted to a range where KF = 60 or less as described above. Because of the fact that it is installed in K, there is no influence of gas on the impeller, and as a result, the amount of gas that can be supplied increases, compared to air seas of the same size.
The amount of treated liquid increases in the evening, improving aeration performance. .

・Although the above embodiment uses an axial flow impeller,
A diagonal flow impeller or a spiral impeller may be used, and a submersible motor may be used instead of a submersible geared motor. Furthermore, in the above embodiments, a diffuser pipe with holes in the pipe is used as the gas supply means, but other means, such as the outer circumferential surface of the casing (the diffuser tube mounting surface in the embodiment) or the inner circumferential surface of the casing, are used as the gas supply means. It is also possible to make holes on the surface (the surface facing the outer peripheral surface and the flow path), to have a punching plate with holes in it, or to have slit-like holes.
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[Brief explanation of drawings]

FIG. 1 is a front view showing a part of a conventional bottom discharge type aeration device in cross section, and FIG. 2 is a cross section showing the left half of a bottom discharge type aeration device according to the bottom discharge type aeration invention. Front view shown, 4th
The figure and FIG. 5 are explanatory diagrams showing the difference in n6 between the lower discharge type and lower discharge type aeration devices. 1.■.Casing, 2..-.Underwater gear motor ^3
... Impeller, 4 e... Motor support, 5...
・Air diffuser pipe, 6... air diffuser hole, 7... air supply pipe, 8...
・Fist/Air supply port, 9... - Suction port, 10... Discharge date and time Applicant Ebara Corporation Figure 1 Figure 4 Figure 5

Claims (1)

[Claims] (1) Used in an aeration tank, the impeller axis is vertical, the flow direction inside the impeller is from top to bottom, and the front is diagonally downward from top. The flow path is shaped like an umbrella nozzle, and the position of the diffuser port for supplying gas into the processing liquid is set so that the angle between the meridional streamline from the impeller to the discharge port and the horizontal melt is 60 or less. Range!
An aeration device characterized by a PIK installed. (#) Set the ratio of the distance on the calf surface streamline from the diffuser port position to the discharge port to the height H of the impeller to be 0.5≦4≦
2.5 The aeration device according to claim 1.