JP3508571B2 - Pressure flotation device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized flotation apparatus for flotation-separating a suspended substance from water containing the suspended substance, and more particularly to an apparatus to be treated. The present invention relates to a pressurized flotation device configured to supply water into a tank body by a rotating distributor. 2. Description of the Related Art A distributor is provided in a tank so as to be swivelable, and while the distributor is swirled, mixed water of raw water and pressurized water flows out of the distributor into the tank to remove suspended substances. As a pressurized flotation device designed to float and separate in the body,
There is one described in JP 23668. [0003] The distributor of the same publication has a tubular wastewater distribution arm extending in the radial direction of the tank body, and a water outlet pipe projecting below the wastewater distribution arm (this water outlet pipe is provided with the water outlet pipe). A plurality of the arms are provided at intervals in the longitudinal direction of the arm) and an opening for water outflow provided on a side surface of the water outlet pipe. [0004] A plurality of the openings are provided on the side surface of the water outlet pipe extending in the up-down direction at an interval vertically. Further, this opening is open toward the front side in the turning direction of the distribution arm (FIG. 4 of the same publication). [0005] When the water outlet is provided so as to open toward the upstream side in the turning direction of the distributor as in the prior art, the outflow from the opening is liable to be disturbed, and the suspended matter becomes finer or bubbles are generated. Is separated from the suspended substance, thereby lowering the separation efficiency. In order to solve such problems and to provide a pressure flotation device excellent in separation efficiency, the present applicant firstly provided a tank having an annular peripheral wall and a central portion of the tank. A distributor extending in a radial direction from the central portion and capable of turning around the central portion in the tank body, a turning drive device of the distributor, and a means for supplying a mixed water of raw water and pressurized water into the distributor. And a pressurized flotation device provided with a mixed water outlet provided in the distributor and opened toward the downstream side in the rotational direction (Japanese Patent Application No. 9-209, 1993).
-80309. Hereinafter, it is referred to as “first application”. ). In the pressure flotation device of the prior application, the water flows from the distributor toward the downstream side in the distributor turning direction, so that the flow of the water is not easily disturbed. For this reason, the suspended substance is prevented from being finely divided and bubbles are prevented from being detached, so that efficient flotation separation processing is performed. In the pressure flotation device of the prior application, the upper end of the distributor is positioned at least 10 cm below the water surface, for example, 20 to 50 cm below the water surface, in order to efficiently perform solid-liquid separation. Is preferred. In the above-mentioned pressure flotation device of the prior application, the mixed water of the raw water and the pressurized water is discharged from the mixed water outlet of the distributor immersed in water, and the suspended substance and the treated water are mixed. However, in order to improve the quality of treated water in the pressure flotation device of the prior application,
It is desired that the flow of the mixed water of the raw water and the pressurized water discharged from the mixed water outlet of the distributor and the flow of the water in the tank are not disturbed by interference with each other. That is, when the flow of the water is disturbed, micro air bubbles (micro air) generated from the pressurized water are associated with each other and become difficult to be adsorbed on the suspended matter, or the micro air once adsorbed on the suspended matter is re-disturbed by the turbulent water. The separation causes troubles such as deterioration of the floating property of the suspended substance, and prevents efficient floating separation. According to the present invention, in the pressure flotation device of the prior application, the flow of the mixed water discharged from the mixed water outlet of the distributor and the flow of the water in the tank body are reliably prevented, and the suspended substance By effectively performing flotation separation,
An object of the present invention is to provide a pressurized flotation device capable of stably obtaining treated water having good water quality. According to the present invention, there is provided a pressure flotation device comprising: a tank having an annular peripheral wall; a tank extending radially from a center of the tank; A distributor capable of pivoting around the inside of the tank, a pivot driving device for the distributor, means for supplying mixed water of raw water and pressurized water into the distributor, and a downstream side in the rotational direction provided in the distributor. And a mixed water outflow opening that opens toward the container, wherein the mixed water outflow provided in the distributor is located at a water depth of 3 to 18 cm in the tank body .
And the outflow velocity of water from the mixed water outlet is 5 to 15 cm.
/ Sec and the rotational speed of the distributor
Degree is characterized by 1~3m / min der Rukoto. In other words, the present inventors have made it possible to reliably prevent the flow of mixed water discharged from the mixed water outlet of the distributor and the flow of water in the tank in the above-mentioned pressure flotation device, As a result of intensive studies to efficiently perform the floating separation of suspended solids, it was found that the discharge position of the mixed water of the raw water and the pressurized water into the tank greatly affected the turbulence of the water flow. If the water depth at the outlet of the mixed water of the distributor is too shallow and too close to the water surface, the suspended substance (scum) which floats due to the rotation of the distributor body or the blowing of the mixed water is easily disturbed, and the scum emits bubbles. And the quality of the treated water deteriorates. Conversely, if the depth of the mixed water outlet of the distributor is too deep, the upward flow of the mixed water becomes turbulent, and micro air is separated during the scum floating process, so that the quality of the treated water also deteriorates. By disposing the mixed water outlet of the distributor at a depth of 3 to 18 cm in the tank according to the present invention, disturbance of the mixed water and water in the tank is prevented, and scum floating and solid-liquid separation are performed. Can be performed efficiently, and as a result, it is possible to improve and stabilize the quality of treated water. In the present invention, the water depth in the tank at the outlet of the mixed water outlet of the distributor is the distance from the water surface to the upper end (top) of the opening of the outlet of the mixed water outlet, as shown in FIG. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1A is a longitudinal sectional view of a pressure flotation device according to an embodiment, and FIG. 1B is a plan view of the same. FIG. 2 is an enlarged view of the distributor. The tank body 1 having an annular peripheral wall is formed in a conical shape in which the bottom is lower toward the center, and the pit 1 is formed in the center.
a is provided. Raw water supply pipe 2 from this pit 1a
Is started up halfway in the tank body 1. A pressurized water supply device (not shown) is connected to the raw water supply pipe via a valve 3. A water collecting pipe 4 is provided below the tank body 1. The water collecting pipe 4 is a tubular member that circulates along the peripheral wall of the tank body 1, and is provided with a hole-shaped water collecting port at predetermined intervals in the longitudinal direction. In addition, this water collecting port may be provided on any of the upper surface, the side surface, and the lower surface of the water collecting pipe 4. However, it is preferable to provide the water collecting port on the lower surface side so that the inflowing raw water is hardly short-circuited. Reference numeral 4a denotes a water collection drain pipe connected to the water collection pipe 4. A connecting part (center cage) 10 of the distributor 5 is fitted on the upper end of the raw water supply pipe 2. The four distributors 5 extend in the radial direction of the tank body 1, and the distributors 5 are assembled (connected) at the center of the tank body 1. The connecting portion 1 having a cylindrical shape is formed downward from the collecting portion of the distributor 5.
0 is protruding. The distributor 5 is turned inside the tank 1 by a motor 8. An opening 6 for water outflow is provided in the distributor 5 so as to face the wake in the turning direction. A skimmer 7 for scraping the floating scum is provided near the water surface of the tank body 1. The gap 7 is also rotated (turned) integrally with the distributor 5 by the motor 8. Alternatively, a reverse gear may be provided on the motor 8 so that the distributor 5 and the skimmer 7 can be rotated in opposite directions by a double shaft. A scum outflow portion 9 a and a trough 9 are provided on a part of the peripheral wall of the tank body 1. The pit 1a is connected to a sludge discharge valve 11. In the pressurized flotation apparatus of this embodiment, a gap of about 2 to 5 mm is provided between the outer periphery of the upper end of the raw water supply pipe 2 and the inner periphery of the connecting portion 10. Reference numeral 2 is inserted into the communication section 10 by about 10 to 30 cm. As shown in FIG. 2, the distance D between the water surface W of the tank 1 and the upper end (top) 6a of the water outflow opening 6 of the distributor 5 is 3 to 18 cm. If the distance D is less than 3 cm, the floating scum is disturbed by the rotation of the distributor 5 and the outflow of water from the opening 6, and bubbles are released and settled, so that the quality of the treated water tends to deteriorate. Conversely, when the distance D exceeds 18 cm, the upward flow of water flowing out of the opening 6 becomes a turbulent state,
Micro air separation from scum occurs during the ascent process,
After all, the quality of the treated water tends to deteriorate. The setting of the water depth can be performed, for example, as follows. At the time of designing the pressure flotation device, the design is made such that the set water level in the tank and the distributor have a predetermined positional relationship. The configuration is such that the height of the distributor can be freely changed. For example, a distributor is provided movably in the height direction on a rotating shaft, and the position of the distributor is adjusted according to the water level in the tank. For example, in the case of the pressurized flotation device shown in FIG. 1, the fitting depth between the communication part (center cage) 10 of the distributor 5 and the upper end of the raw water supply pipe 2 is configured to be variable. The water level in the tank can be changed freely. For example, the water depth of the distributor is adjusted by starting up the treated water discharge pipe and making the position of the upper end thereof variable so that the water level can be adjusted. Among the above methods, the above method is a preferable method because it can easily cope with a change in the amount of treated water. Although the present invention is not particularly limited, when the tank body 1 has a processing capacity of 15 to 25 m ³ / Hr,
The diameter of the opening 6 is about 5 to 7 cm.
A total of about 20 to 28 pieces are provided in the book distributor 5, and the outflow velocity of water from the opening 6 is 5 to 15 cm / sec.
c. In order to prevent the water in the tank 1 from rotating together with the distributor 5 and the skimmer 7 to form turbulence, the rotation speed (peripheral speed) of the distributor 5 and the skimmer 7 is set to about 1 to 3 m / min. You. In the present invention, as shown in FIG. 4, a flow straightening plate 12 may be provided from the upper part of the distributor 5 to the downstream side (ie, so as to protrude above the opening 6). The width of the current plate 12 is preferably about 120 to 180 mm. Further, it is preferable that the current plate 12 be provided with a gradient of about 1/20 to 1/30 so that the current plate 12 becomes lower as the distance from the distributor increases. In the present invention, it is preferable to provide a bubble bleeding hole having a diameter of about 3 to 8 mm at the tip of the distributor 5 in order to extract the air remaining in the distributor 5. The present invention will be more specifically described below with reference to examples and comparative examples. Examples 1 to 6 and Comparative Examples 1 to 3 The levitation separation was performed by the pressure levitation apparatus shown in FIG. After adding an inorganic coagulant to raw water (industrial water) to generate flocs, mixed water obtained by mixing pressurized water with about 20% of raw water is
The liquid was released from the opening 6 through the distributor 5 through the connecting part 10, and a solid-liquid separation of the suspended substance (scum) and the treated water was performed (the target value of the treated water quality was SS 4 mg / L). At this time, the distributor 5 is moved up and down to change the water depth (distance D) of the opening 6, the treated water is sampled and the SS is measured, the relationship between the water depth of the opening 6 and the treated water SS is examined, and the results are displayed. 1 and FIG. The apparatus specifications and processing conditions other than the water depth at the opening of the distributor were as follows. Processing capacity of tank 1: 20 m ³ / Hr (including pressurized water volume) Diameter of openings 6: 6 cm Number of openings 6 (total): 24 Outflow velocity of water from openings 6: 8 cm / sec Distributor 5 And the rotation speed (peripheral speed) of the gap 7: 2.5 m / min. The distance between the distributor 5 and the water collecting pipe 4: 120 cm. The height (depth) of the tank body 1: 150 cm. From Table 1 and FIG. 3, it is understood that when the water depth of the opening of the distributor is 3 to 18 cm, treated water having good water quality can be obtained. As described in detail above, in the pressurized flotation device of the present invention, turbulence in the tank is prevented, efficient flotation is performed, and high-quality treated water is obtained stably. Can be. This pressure flotation device has a relatively simple configuration and requires only a low tank body.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view and a plan view of a pressure flotation device according to an embodiment. FIG. 2 is an enlarged view of a distributor. FIG. 3 is a graph showing the results of Examples 1 to 6 and Comparative Examples 1 to 3. FIG. 4A is a perspective view of a distributor of a pressure flotation apparatus according to another embodiment, and FIG. 4B is a cross-sectional view of the distributor of FIG. [Description of Signs] 1 tank body 2 raw water supply pipe 3 pressurized water valve 4 water collecting pipe 5 distributor 6 opening 7 skimmer 8 motor 9 trough

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Claims (1)

(57) [Claim 1] A tank body having an annular peripheral wall, extending radially from a center portion of the tank body, the tank body centering on the center portion. A distributor for rotating the distributor, a driving device for rotating the distributor, means for supplying mixed water of raw water and pressurized water into the distributor, and a mixed water flow that opens toward the downstream side in the rotational direction provided in the distributor. A pressurized levitation device comprising an outlet, wherein the mixed water outlet provided in the distributor is disposed at a depth of 3 to 18 cm in the tank body.
And the outflow velocity of water from the mixed water outlet is 5 to 15 cm / s.
ec, and the rotational speed of the distributor is 1 to 3 m / m.
in der Rukoto on the dissolved-air flotation device according to claim.