JP2527334Y2 - Settling tank - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a sedimentation tank for collecting sludge in a sedimentation tank in the center with a scraping blade (rake) of a sludge collector. In order to improve efficiency, the slope (tilt angle) at the bottom of the settling tank,
The present invention relates to an eccentric cone and an eccentric elliptic cone settling sludge transfer device provided in a collecting chamber provided at the bottom center of a settling tank.

[Prior Art] In a conventional large-scale sedimentation tank, if the inclination of the bottom of the sedimentation tank, which is inclined from the cylindrical outer peripheral wall of the sedimentation tank toward the center of the mud collector, is increased, the water depth in the center becomes large, and Sludge stays in the sedimentation tank in an oxygen-free state for a long time, and part of the settled biological sludge is killed, generating digestion gas, or a large mass of sludge (floc) is generated by nitrogen gas adhesion by the denitrification reaction. Because it rises, it cannot take a large gradient.
When the slope at the bottom of the sedimentation tank is small and the concentration of sludge flowing into the sedimentation tank is high, it is known that the transfer amount is doubled by providing two rake arms on a cloth at the center of the sedimentation tank. The quantity is not enough.

The sludge discharge port of the central mud collection chamber has one or more discharge pipe ports opened from the circumference of a vertical cylinder having a bottom.

[Problem to be Solved by the Invention] Let us consider a case where the bottom of the settling tank is equally divided into six concentric circles. The outermost circular circle is the sixth circular circle, the inner circular circle is the fifth circular circle, and the inner circular circle is the sixth circular circle. The annular circle is referred to as a fourth annular circle... The center circle is referred to as a first annular circle. The sludge settled in each annular circle by the rotation of the stirring arm is not left behind, and the first sludge is sequentially moved from the outermost annular circle to the center without mixing.
It is good to be sent to an annular circle, mud collection room. For this purpose, it is desirable that the amount of sludge transferred by the rake of the inner annular circle by one rotation of the stirring arm be 1.1 to 1.2 times the amount of sludge transferred by the outer annular circle. The transfer amount of the sludge collection lake (referred to as the first sludge collection lake) of the first annular circle at the center is about 1.8 to 2.5 times the amount of sludge collected at the outermost annular circle collection lake. It is desirable to be able to transfer to the sludge discharge port of the room. In order to satisfy this condition, the area of the first mud rake is at least 2.5 times the area of the sixth rake if the first and sixth rakes are at the same angle to the stirring arm. It is necessary to have a large area and to transport the sludge several times the distance to the center of the sixth rake to collect sludge in the center. In order to transfer to the center with the rake (several pieces) of the first circular circle, in which the rotation distance of the rotation of the stirring arm is shorter than that of the sixth rake, the angle between the stirring arm and the first rake (the included angle) ) Must be smaller than the rake of the sixth annular circle. This often makes it difficult to transfer the sludge to the center due to poor sliding between the rake surface and the sludge, and the sludge density is increased by kneading (kneading) the sludge in the first annular circle. Since the sludge is not smoothly transferred from the outer peripheral portion toward the center, the sludge mass having a long residence time floats in the first to third annular circles. In addition, the sludge that reaches the entrance of the central collection chamber is kneaded (kneaded) at the entrance of the collection chamber to increase the sludge density, and the stirring arm of the stirring shaft of the collection chamber rotates. Because the rotation speed is low, the compacted sludge adheres to the arm and rotates, and if the number of suction pumps in the collection chamber is small, a water streak is formed from the entrance of the collection chamber to the suction port of the discharge pump. There was a problem of short circuit transfer.

The present invention aims to ensure that even large sedimentation tanks and highly concentrated sludge are transported without consolidation to the discharge port of the central sludge collection chamber, and that the sludge arm and the central sludge that homogenize the sludge by rotation at the central discharge port. Provide room.

[Means for Solving the Problems] The sedimentation tank in the present invention has a sludge bottom slope from the circumference of a circle area not more than half of the sedimentation tank water area toward the center axis of the sedimentation tank. It has an angle of more than 4 to 41 degrees, and the bottom has a structure that slides the settled sludge into the mud collection chamber, and the rake has a structure that rotates along the bottom with a different slope. The sludge transfer amount can easily reach several times the outermost sludge transfer amount due to the sludge sliding down to the center due to the rake agitation. The angle of repose depends on the type of sludge, its concentration,
It is governed by the material of the precipitation tank and the smoothness of the bottom of the precipitation tank. If the bottom of the settling tank is an iron plate, the concentration of the settling sludge is ³ to 7 kg / m ³ , and the sludge load of the aeration tank at the entrance of the settling tank is 0.15 kg / kg day or less, the angle of repose is in the range of 3 to 25 degrees. If the aeration tank sludge load at the entrance of the settling tank is 0.25 kg / kg day or more, the angle of repose is in the range of 5 to 40 degrees.

The mud collection chamber provided at the center of the bottom of the settling tank has a bottomed cylindrical shape (No. 3).
(Fig. 4) or a wide-opened triangular corvette with a bottom (Fig. 4), and the entrance of the mud collection chamber is open at the portion where the bottom of the sedimentation tank having an inclination angle equal to or greater than the angle of repose contacts the side wall of the mud collection chamber. The entrance of the mud collection chamber is relatively large, and a cone or elliptical cone eccentrically fixed to the stirring blades and the rotating shaft for sludge sliding down into the mud collecting chamber is provided on the side wall of the mud collecting chamber by rotation of the rotating shaft. It has a structure that discharges the sludge to the suction port of the pump.

[Action] When the conventional sedimentation tank collects sludge from the outer periphery to the center with a rake, the amount of sludge to be transported increases toward the center and the rotation distance of the rake is short despite the transport distance being longer than the outer periphery. Therefore, if the angle between the rake and the stirring arm is reduced to increase the efficiency of transferring sludge to the center, the sludge and rake slip and the efficiency of transferring sludge to the center decreases. And the sludge is kneaded (kneaded) in this area
Will do.

On the other hand, the amount of sludge transfer increases,
By setting the inclination angle of the bottom of the sedimentation tank within the water area within the angle of repose to be more than the angle of repose, the sludge slides down the bottom without the raking action of the rake. Can be transported.

The area of the entrance of the mud collection chamber is set to 1/8 to 1/70 of the area of the sedimentation tank, so that the sludge can easily slide into the mud collection chamber.

The stirring blades of the mud collection chamber are fixed to a common rotation shaft with the rotation shaft of the mud collector, and are installed in the direction in which the sludge is sent by rotation to achieve a uniform sludge concentration in the mud collection chamber.

In addition, by providing an eccentric cone or an eccentric elliptical cone fixed to the stirring shaft, the porosity in the mud collection chamber is reduced, the residence time of the sludge is shortened, and the eccentric cone and the eccentric elliptical cone are formed. Due to the rotation, the sludge can be quickly sent out to the suction port of the delivery pump provided on the side wall of the mud collection chamber.

Example An example will be described with reference to the drawings.

1 to 5, the sedimentation tank is made of metal or concrete. The bottom is composed of a relatively gentle bottom (3) and a steep bottom (2), and an overflow gutter (9) is provided around the conical bottom (3) with a gentle slope. In a shallow cylindrical or square sedimentation tank (10), there is a sludge pipe (8) for feeding the undiluted solution (referred to as sludge) at the center. Sludge from the sludge pipe settles, and the sludge settles. The rake (5) fixed to the arm (6) collects it at the bottom (3).

The sludge coming to the steep bottom (2) slides down the bottom by the rotation of the rake, and the sludge reaches the entrance of the central sludge collection chamber (4). The area of the mud collection room entrance is 1/8 of the area of the sedimentation tank
If it is up to 1/70, the sludge that falls down can be accepted in the mud collection room without being concentrated.

Due to the rotation of the stirring blades (11) fixed to the stirring shaft and the eccentric cone (12), the sludge that has fallen into the collection chamber is not concentrated and the suction port (7) of the delivery pump on the side wall is immediately concentrated. ) And is discharged. The fixed position of the eccentric cone and the eccentric elliptical cone is the ratio of the distance from the intersection of the long diameter of the ellipse and the circumference to the stirring axis on the cone bottom parallel to the vertex and the bottom of the mud collection chamber, 1: 2 ~ 1: 9, long diameter 0.5 ~ 0.95
It is desirable that

[Effects of the Invention] Since the present invention is configured as described above, the following effects can be obtained.

In the sedimentation tank having a steeper slope than the angle of repose of the sludge according to claim 1, the bottom of the sedimentation tank is directed toward the center axis of the sludge collector from a circumferential part having a circular area smaller than 1/2 of the water area of the sedimentation tank. Since the sludge has a steep slope than the angle of repose, the sludge can slide down the steep slope at the bottom by the rotation of the brake, and the sludge can be easily transferred to the entrance of the sludge collecting chamber.

When the sludge of claim 2 has an eccentric cone and an elliptic long diameter of the eccentric elliptical cone bottom of 0.5 to 0.95 of the diameter of the sludge collection chamber, the sludge retention time in the sludge collection chamber is shortened, and the sludge concentration can be increased. Disappears.

The stirring shaft fixed position on the bottom is lowered by rotating by setting the ratio of the distance from the intersection of the elliptical long diameter and the circumference to the stirring shaft to 1: 2 to 1: 9. Incoming sludge can be reliably sent to the suction port of the dispensing pump that sequentially opens on the side wall of the mud collection chamber.

[Brief description of the drawings]

1 is a longitudinal sectional view of a sedimentation tank, FIG. 2 is a transverse sectional view of the sedimentation tank, FIG. 3 is a sectional view of a main part of a cylindrical collecting mud chamber having a bottom, and FIG. Sectional view of the main part of the mud chamber, Fig. 5 shows the fixed position of the stirring shaft on the bottom of the eccentric cone and eccentric elliptic cone, 1 ... sedimentation tank, 2 ... steep bottom, 3 ... bottom, 4 ......
Sludge collection chamber, 5 rake, 6 stirring arm, 7 discharge (pump) suction port, 8 sludge supply cylinder, 9 overflow weir, 10 sedimentation tank, 11 Stirring blades, 12: Eccentric cone (eccentric elliptic cone), 13: Stirring axis

Claims (2)

(57) [Scope of request for utility model registration] In a sedimentation tank in which a sludge collector moves in a circle, the bottom of the sedimentation tank has a relatively gentle slope (3), and a circle smaller than half the water area of the sedimentation tank. Center)
From the circumference of the area, the steep bottom (2) having a steep slope of 4 to 41 degrees toward the central axis of the mud collector is joined, and the steep bottom and the side wall of the mud collection chamber (4) are in contact. The sedimentation tank has a structure that opens at and the rake of the mud collector rotates along the bottom with different slopes. 2. A mud collecting chamber, wherein a rotating shaft of the mud collector is used as a stirring shaft, and an eccentric cone and an eccentric elliptical cone fixed to the shaft are provided.
The fixed position is the ratio of the distance from the intersection of the major axis of the ellipse to the circumference at the apex and base of the cone or elliptical cone to the stirring axis within the range of 1: 2 to 1: 9, The sedimentation tank according to claim 1, further comprising a settling sludge transfer device having a range of 0.5 to 0.95 with respect to the diameter of the collection chamber.