JPH08173987A - Aeration apparatus suitable for tank with high depth of water - Google Patents

Abstract

PURPOSE: To guide a water flow and bubbles for aeration, generated by a screw, surely to the bottom and inner wall surface of a tank and to perform stable, efficient aeration-agitation by attaching a conical flow-straightening cone to the inside of the lower end of a draft tube installed below the screw and an inverted-conical guide to the periphery of the screw. CONSTITUTION: An apparatus is composed of a draft tube 2 installed in a treatment tank 1, a screw type aerator 3 placed above the draft tube 2 to face it, a conical flow-straightening cone 4 which is attached to the lower end of the draft tube 2 and guides an air-mixed water flow generated by the rotation of a screw to the bottom of the tank, and a inverted conical guide 5 which is fixed around the tube 2 and guides bubbles discharged from the lower end of the tube 2 to an area apart from the periphery of the tube 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerator for aeration and stirring in a deep water tank more effectively and uniformly.

[0002]

2. Description of the Related Art In sewage treatment, it has recently been difficult to secure a land for a treatment plant in the suburbs of a large city. For this reason, high-deep tanks are used because a large amount of sewage treatment is carried out on a small site. When sewage (sewage) is aerated using a screw type aerator when treating sewage (sewage) by aerobic fermentation in this deep water tank, the aerator alone generates a circulating water flow in the vertical direction in the entire deep water tank and stirs it. Since it is difficult to do so, the draft tube that reaches the bottom of the screw type aerator is installed in the same vertical position below the screw type aerator, and the screw type explosive machine and the draft tube are used in combination. The mixed water flow generated in 1. is guided to the bottom of the tank by a draft tube so that stirring and aeration reach the bottom of the tank.

[0003]

However, the draft tube is arranged on the same line as the screw of the screw type aerator, and the screw of the aerator is inserted into the upper end of the draft tube to stir the waste water in the draft tube. However, since the air is aerated, it is necessary to make the flow velocity at the inlet of the draft tube exceed the rising velocity of bubbles. Therefore, the air bubbles discharged from the lower end of the draft tube (discharging port) thus constructed into the inner bottom portion of the water tank together with the water flow have a large air lift force. Therefore, as shown in FIG. Immediately ascends at the outlet and rises to the water surface of the tank through the water area along the outer circumference of the draft tube. Therefore, not only does the mixed-air flow reach the bottom of the tank, but the mixed-water flow does not reach near the inner wall of the tank, and a circulating water flow is generated only near the draft tube in the center of the tank, and the agitation of the entire tank I can't do it. To improve this, it is conceivable to lengthen the draft tube so that it is close to the bottom of the tank, but there is a limit to the length of the draft tube. Acts, it is difficult to obtain the flow-down velocity required to flow the bubbles, an unstable operating state occurs, and efficient stirring and aeration cannot be performed over the entire tank. Further, it is necessary to increase the aeration power.

According to the present invention, a rectifying cone having a conical shape is provided in the lower end of a draft tube disposed below the screw, and a guide having an inverted conical shape is provided at an outer peripheral portion thereof. The purpose of this method is to reliably guide the air bubbles to the bottom of the tank and the inner wall surface of the tank to perform stable and efficient aeration and stirring.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and comprises a draft tube provided in a processing tank and a screw type aerator above the draft tube and opposed thereto. , A cone-shaped rectifying cone for guiding the mixed water flow generated by the rotation of the screw to the bottom of the draft tube to the bottom of the draft tube, and the bubbles provided on the outer circumference of the draft tube and discharged from the bottom of the draft tube. Draft tube outer surface Consists of a guide with a conical shape, a pyramid shape, etc. that is inverted upside down to guide it farther from the water area, so that even in deep water tanks, up to the inner wall surface and bottom of the tank The main point is to ensure aeration and stirring.

[0006]

[Operation] A cone-shaped rectifying cone is installed at the lower end of the draft tube opposite the screw-type blasting machine, and an inverted cone-shaped guide is installed above the rectifying cone on the outer periphery of the draft tube. Since each of them is arranged, the energy flow of the downward mixed water flow in the draft tube generated by the rotation of the screw can be minimized and it is discharged from the lower end of the draft tube. When the mixed air flow flows down along the outer peripheral surface of the flow rectifying cone, the mixed air flow becomes high speed because the discharge port area at the lower end of the draft tube is made into a ring-shaped small area by the flow rectifying cone. For this reason, the downward flow of the air-fuel mixture is discharged from the draft tube at high speed, so it reliably reaches the bottom of the tank,
Aeration and stirring can be performed up to the bottom of the deep water tank.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An aeration apparatus suitable for a deep water tank of the present invention will be described below with reference to the embodiments shown in the drawings. In the figure, 1 is a treatment tank for aerobically treating sewage or sewage, and this treatment tank 1 has a water depth of several meters or more, and has a predetermined diameter and length predetermined inside the treatment tank 1. Draft tube 2 provided with is arranged so as to be substantially vertical, and the lower end of draft tube 2 is discharge port 2 opening toward the tank bottom.
b. The upper end opening surface 2a of the draft tube 2 is provided so as to be located in water having a predetermined depth from the normal treated water surface WL.

At the lower end discharge port of the draft tube 2, a conical rectifying cone 4 is provided. This rectifying cone 4 has a conical shape with a required angle. The tip of the rectifying cone 4 is inserted into the discharge port of the draft tube 2 or is faced as shown, and the lower part of the rectifying cone is the draft tube. It is fixed to the bottom of the tank so as to have a diameter larger than the diameter and to project outward from the outer peripheral surface of the lower end of the draft tube. A gap is formed between the lower end peripheral surface of the draft tube and the flow rectifying cone 4 in the circumferential direction as shown in the drawing. In this way, the mixed water flow at the outlet of the draft tube is guided to the peripheral surface of the rectifying cone and smoothly guided to the bottom of the tank. The rectifying cone 4 may have a pyramidal shape instead of a conical shape.

Reference numeral 3 in the drawing denotes a screw type aerator, which is fixed to a pedestal 5 or the like provided at the upper part of the processing tank, the screw shaft 31 is vertically projected below the water surface, and the lower end of the screw shaft is for aeration and stirring. Install the screw 32 of. This screw type aerator 3 is formed by attaching a screw 32 to the lower end of a hollow screw shaft attached to a motor. The screw is rotated by driving the motor to stir and push the water in the water region at the tip of the screw and A negative pressure is generated in the tip water area, and the negative pressure is used to suck the atmosphere from the intake port at the upper end of the hollow screw shaft, discharge it to the water area at the lower end of the screw, and mix with water.

The tip surface of the screw 32 is shown in FIG.
As shown in, the draft tube 2 and the aerator 3 are arranged in a relative positional relationship so as to substantially coincide with the horizontal line of the upper end opening surface of the draft tube 2. Of course, the longitudinal axis of the screw and the draft tube axis are aligned, that is, the screw is aligned with the center of the draft tube.

Further, a guide 5 having an inverted conical shape, a funnel shape (an inverted umbrella shape), an inverted pyramid shape, or the like is provided on the lower outer circumference of the draft tube 2. When the bubbles in the mixed water flow discharged from the discharge port 2b at the lower end of the draft tube float up against the flow velocity of the water flow, the guide 5 is located outside the outer peripheral water region of the draft tube, preferably in the inner wall surface water region of the tank. It is designed so that it will rise toward the surface of the water after it has been guided up to. Therefore, this guide 5 prevents the air bubbles from flying straight up and guides it to the water area farther from the draft tube so that its outer diameter is determined by its relationship with the inner diameter of the tank, and its inclination angle also rises. It is determined so that it will be transported to the outside of the draft tube while being guided to the surface.

A through hole 5a is formed in the center of the guide 5, and the draft tube 2 is inserted into the through hole 5a, and the solid content settled on the upper surface of the guide through the gap between the through hole and the draft tube is the bottom of the tank. Let it slide down naturally.

In the illustrated embodiment, the guide 5 is supported together with the draft tube by a plurality of columns 6 projecting from the flow rectifying cone 4, but other supporting methods are also possible.

When the aerator 3 is driven in the device constructed as described above, the water in the downstream region of the screw is agitated by the rotation of the screw, and a downward water flow is generated in the draft tube, and the inside of the draft tube is generated. While flowing down, it absorbs water from the water area above the draft tube and is sent into the draft tube. At this time, the atmosphere is sucked by the negative pressure in the water area at the lower end of the screw and mixed as fine air bubbles. This mixed water flow flows down the draft tube and is discharged from the lower end discharge port 2b of the draft tube. Along the outer peripheral surface of the cone-shaped flow rectifying cone 4, the flow is inclined downward and further flows down to reach the bottom layer in the tank.

However, although the buoyancy of the bubbles in the effluent flow differs depending on the particle size, the tiny buoyancy of the bubbles is small and they can reach the bottom of the tank by riding on the effluent flow. The buoyancy also increases when the bubbles have a medium or large particle size. The relatively large bubbles that float up against the flow velocity of the flowing water flow upward in the water area near the draft tube. The buoyant force of the rising bubbles is blocked by the guide 5 having an inverted conical shape, the floating speed is slowed, and the bubbles are further moved to the outside of the draft tube along the inclination of the guide 5 to guide the bubbles. It is released from the outer peripheral edge of and floats up in the water. This makes it possible to prolong the residence time of bubbles in water.

The mixed water flow discharged from the lower end of the draft tube in this way rides on this water flow and reaches the bottom of the tank,
Even if a large bubble floats against the flow of water, it is guided into the tank farther from the outer circumference of the draft tube by the inverted cone-shaped guide 5 provided on the outer circumference of the draft tube, and rises in the water area of the inner wall surface of the tank. However, it is possible to suppress the air lift force at the draft tube outlet, and by continuously performing this, the draft tube flows down into the tank, and an upward flow occurs in the water area away from the outer circumference of the draft tube. Circulating water flow is generated in the entire tank and stirring is possible.

When the water is sucked from the suction port 2a at the upper end of the draft tube 2, it is sucked from the longitudinal axis of the screw shaft due to the characteristics of the screw, and is not sucked from the outer peripheral water area of the screw. Moreover, this screw 32
Is set at a predetermined water depth position from the water surface WL, so that air bubbles floating at or near the water surface at the outer peripheral portion of the draft tube are not sucked into the draft tube. For this reason, no difference in gas-liquid density occurs at the screw position in the draft tube, so that the screw propulsion force is stable and stable operation is performed.

[0018]

The aerator suitable for the deep water tank of the present invention is
Generated by a screw because a cone-shaped rectifying cone is installed at the lower end of the draft tube installed in the treatment tank in confrontation with the screw type explosive machine, and an inverted cone-shaped guide is installed on the outer periphery. The mixed air flow made possible flows down in the draft tube and is guided to the flow straightening cone at the discharge part at the lower end of the draft tube to guide the mixed air flow to the bottom of the tank.
Bubbles that float in this way in the water flow are also prevented from floating in the direct upward direction by the inverted cone-shaped guide and are guided toward the inner wall surface of the tank, so that the floating time and retention time of the bubbles are lengthened, improving the oxygen dissolution efficiency, There is an advantage that the stirring and aeration efficiency can be improved by promoting the stirring flow without inhibiting the stirring force of the screw.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an aeration apparatus suitable for a deep water tank of the present invention.

FIG. 2 is a cross-sectional view of a known example.

[Explanation of symbols]

 1 Treatment Tank 2 Draft Tube 2a Suction Port 2b Discharge Port 3 Aerator 31 Screw Shaft 32 Screw 4 Commutation Cone 5 Guide

Claims (1)

[Claims] 1. A draft tube provided in a processing tank,
Above the draft tube, a screw type aerator is installed opposite to the draft tube, a cone-shaped straightening cone for guiding the mixed water flow generated by the rotation of the screw to the bottom of the draft tube, and a draft. An aeration device suitable for a deep tank, comprising an inverted cone-shaped guide which is provided on the outer circumference of the tube and guides bubbles released from the lower end of the draft tube to a position farther from the water area on the outer circumference of the draft tube.