Floating separation device

Abstract

To provide a floatation / separation device having excellent treatment efficiency while allowing its downsizing at the same time.SOLUTION: A floatation / separation device 1 comprising an outer cylinder 3 disposed in the perpendicular direction and an inner cylinder 4 provided with an open upper end positioned approximately in the central section of the outer cylinder 3, with water to be treated being flowed out of the upper end of the inner cylinder 4 allowing the suspended matters to stick to bubbles and to float / separate the same, and the water to be treated removed of the suspended matters being flowed down through a space A disposed between the outer cylinder 3 and the inner cylinder 4, to subsequently be discharged outside the system, is characterized in that a straightening unit 6 for the water to be treated to flow therethrough, is provided in the lower section of the space A, and the straightening unit 6 is formed of a plurality of tilting plates of cylindrical truncated cones each having a different diameter concentrically arranged in such a way that the diameters thereof decrease toward the downward direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flotation separator used as a solid-liquid separation device in water treatment. [Background technology]

[0002] In water treatment for sewage, industrial wastewater, and other types of wastewater, these are separated into solid and liquid components using methods such as flotation separators and sedimentation tanks, after passing through a regulating tank. A flotation separator is a device that separates suspended solids in the treated water by attaching them to bubbles.

[0003] Here, a schematic diagram of a conventional flotation separation device is shown in Figure 4 (see, for example, Patent Document 1). The flotation separation device 21 shown in Figure 4 is a pressurized flotation device that uses pressurized water to generate bubbles. The flotation separation device 21 has a tank body 22, an outer cylinder 23 provided along the inner circumference of the tank body 22, and an inner cylinder 24 provided in the approximate center of the outer cylinder 23. The upper end of the inner cylinder 24 is open, and a supply pipe 25 extending upward from the lower end of the inner cylinder 24 is provided inside. The supply pipe 25 opens upward inside the inner cylinder 24, and a mixture of the water to be treated and pressurized water is introduced from there. When the mixed water is introduced, the air dissolved in the pressurized water becomes bubbles, and suspended solids in the water to be treated adhere to these bubbles, forming flocculated flocs that float to the surface. The water to be treated, from which the suspended solids have been removed, then flows around from the lower end of the outer cylinder 23, rises between the outer cylinder 23 and the tank body 22, and is discharged out of the system.

[0004] In the flotation separator 21, the water to be treated, introduced from the supply pipe 25, flows out from the upper end of the inner cylinder 24 and then descends through the space between the outer cylinder 23 and the inner cylinder 24. The flotation separator 21 is provided with a flow straightening plate 26 to divide this space vertically. The flow straightening plate 26 is provided with multiple flow straightening holes that allow the water to be treated, from which suspended solids have been removed, to pass through. By providing the flow straightening plate 26, the flow of the water to be treated, which flows from the top to the bottom of the space, is straightened, allowing air bubbles to efficiently adhere to the suspended solids, and as a result, the treatment capacity can be improved. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-5519 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Incidentally, although the flotation separator 21 is equipped with a flow straightening plate 26, the speed of the water to be treated descending in the space between the outer cylinder 23 and the inner cylinder 24 (descending speed) varies depending on the location and tends to be non-uniform. That is, the water to be treated that flows out from the upper end of the inner cylinder 24 mainly spreads outwards and reaches the outer cylinder 23, and then flows downward along the wall surface of the outer cylinder 23, so the descending speed near the outer cylinder 23 is greater than the descending speed near the inner cylinder 24. As a result, turbulence may occur. When turbulence occurs, aggregated flocs are broken down and made finer by turbulent agitation. In addition, flocs in areas with high flow rates are more likely to be mixed into the treated water or circulating water without floating, which may lead to a decrease in treatment efficiency.

[0007] On the other hand, the processing capacity of a pressurized flotation device is said to be proportional to the amount of pressurized water that can be supplied. Therefore, the device is often made larger to improve processing capacity, but it is desirable to make it smaller while maintaining processing capacity, due to demands for cost reduction and space saving. However, if the amount of pressurized water is increased while making the device smaller, the upward flow of bubbles generated from the pressurized water and the water flow of the pressurized water will increase, which can easily cause turbulence and lead to a decrease in processing efficiency.

[0008] This invention has been made in view of these circumstances, and aims to provide a flotation separation device that is miniaturized while having excellent processing efficiency. [Means for solving the problem]

[0009] The flotation separation device of the present invention comprises an outer cylinder arranged vertically and an inner cylinder provided approximately in the center of the outer cylinder with an open upper end. The device discharges the water to be treated from the upper end of the inner cylinder, causing suspended solids to adhere to bubbles for flotation separation. The treated water, from which the suspended solids have been separated, is then allowed to descend into the space between the outer cylinder and the inner cylinder before being discharged outside the system. A flow straightening unit is provided at the lower part of the space through which the water to be treated passes. The flow straightening unit is composed of a plurality of frustoconical cylindrical inclined plates of different diameters arranged concentrically and is configured to decrease in diameter towards the bottom.

[0010] The inner cylinder has an inner cylinder tapered portion at its upper end that widens upward, and a frustoconical rectifier plate, which is larger in diameter than the inner cylinder tapered portion, is provided on the outside of the inner cylinder tapered portion so as to narrow downward.

[0011] In the above-described rectifier unit, the inclined plates are arranged such that the distances between them and other radially adjacent inclined plates are approximately equal.

[0012] The above-described rectifier unit is characterized in that the inclination angle of the inclined plate with respect to the vertical direction is within the range of 30° to 50°.

[0013] The outer cylinder is characterized in that it has a tapered outer cylinder portion at its lower end that is narrowed in diameter downwards, and the tapered outer cylinder portion constitutes a part of the inclined plate of the rectifying unit. [Effects of the Invention]

[0014] The flotation separation device of the present invention comprises an outer cylinder and an inner cylinder provided at a substantially central portion of the outer cylinder and having an open upper end, wherein water to be treated flows out from the upper end of the inner cylinder, suspended substances in the water to be treated are attached to air bubbles to be floated and separated, and the water to be treated from which the suspended substances have been separated is lowered into a space between the outer cylinder and the inner cylinder and then discharged out of the system. A flow rectifying unit through which the water to be treated passes is provided at a lower part of the space, and the flow rectifying unit is constituted by concentrically arranging a plurality of truncated conical inclined plates with different diameters, and is arranged to have a diameter decreasing downward. Therefore, by allowing the water to be treated to pass through the flow rectifying unit, the non-uniformity between the descending speed near the outer cylinder and the descending speed near the inner cylinder can be eliminated, and the generation of turbulent flow can be suppressed. In addition, according to this configuration, even when, for example, the device is downsized to increase the circulating water amount (e.g., pressurized water amount), the generation of turbulent flow can be suppressed, and the flotation separation device is excellent in treatment efficiency.

[0015] The inner cylinder has an inner cylinder tapered portion with an increasing diameter toward the upper side at the upper end, and a truncated conical flow rectifying plate having a larger diameter than the inner cylinder tapered portion is provided outside the inner cylinder tapered portion so as to decrease in diameter downward. Therefore, the flow velocity of the water to be treated flowing out from the upper end of the inner cylinder can be moderated, which in turn facilitates eliminating the non-uniformity between the descending speed near the outer cylinder and the descending speed near the inner cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [Figure 1] FIG. 1 is a schematic diagram showing an example of the flotation separation device of the present invention. [Figure 2] FIG. 2 is an enlarged view and the like of the periphery of the flow rectifying unit in the flotation separation device of FIG. 1. [Figure 3] FIG. 3 is a diagram showing the flow of the water to be treated in the flotation separation device of FIG. 1. [Figure 4] FIG. 4 is a schematic diagram showing an example of a conventional flotation separation device. DESCRIPTION OF EMBODIMENTS

[0017] An example of the floating separation apparatus of the present invention will be described with reference to FIG. 1. FIG. 1 is a schematic diagram of the floating separation apparatus, and also shows the internal structure thereof. The floating separation apparatus 1 is a pressurized flotation apparatus that uses pressurized water to generate air bubbles, and is an apparatus that performs solid-liquid separation on water to be treated (raw water). The floating separation apparatus 1 receives, as water to be treated, wastewater such as sewage, industrial effluent and industrial wastewater that has been treated in a conditioning tank or the like, performs a floating separation treatment, and discharges treated water. The treated water discharged from the floating separation apparatus 1 is supplied to, for example, a microbial reaction tank or the like, and is subjected to microbial treatment or the like.

[0018] As shown in FIG. 1, the floating separation apparatus 1 is a vertical cylindrical apparatus disposed along the vertical direction. The floating separation apparatus 1 comprises a tank body 2 having an internal space, an outer cylinder 3 provided along the inner circumference of the tank body 2, an inner cylinder 4 provided at a substantially central portion of the outer cylinder 3, a supply pipe 5 provided inside the inner cylinder 4, a rectification unit 6, a rectification plate 7, a discharge pipe 8 for discharging treated water out of the system, a motor 9, a rotating shaft 10 provided in the vertical direction inside the tank body 2, and an upper blade 11 and a lower blade 12 attached around the rotating shaft 10.

[0019] In the present invention, the floating separation apparatus can be adapted to small to large-sized apparatuses, but it is particularly suitable for small-sized apparatuses because it is excellent in the treatment efficiency of water to be treated even in the case of small-sized apparatuses. For example, the inner diameter φ of the tank body 2 is 1 m to 5 m, preferably 1 m to 3 m. Further, the height of the tank body 2 (the height from the lid portion 2a to the recessed portion 2d) can be, for example, 6 m or less.

[0020] As shown in FIG. 1, the tank body 2 has a lid portion 2a, a cylindrical side wall portion 2b, and a bottom portion 2c. A motor 9 is provided on an upper portion of the lid portion 2a, and the rotating shaft 10 connected to the motor 9 penetrates the lid portion 2a and extends to the bottom portion 2c of the tank body 2. The bottom portion 2c is formed in a mortar shape that is inclined to become lower toward the center, and a recessed portion 2d for accumulating sediment is provided at the center.

[0021] In the flotation separation device 1, the motor 9 drives the rotating shaft 10, causing the upper blade 11 and the lower blade 12 to rotate accordingly. The upper blade 11 is a blade for scraping up scum that has floated to the surface of the liquid. The lower blade 12 is a blade for scraping up sediment that has settled at the bottom 2c and is positioned along the slope of the bottom 2c. The angle of the lower blade 12 can be adjusted as needed by a support member connected to the rotating shaft 10. As the lower blade 12 rotates, the sediment that has settled at the bottom 2c is collected in the recess 2d. The upper blade 11 and the lower blade 12 may also be shaped like feathers or other shapes.

[0022] The outer cylinder 3 is a cylindrical partition wall that divides the space inside the tank body 2, and is suspended and fixed from the lid portion 2a of the tank body 2. The movement of scum that floats to the liquid surface is restricted by the outer cylinder 3, and it is configured so that it does not flow out to the outside. The upper end of the outer cylinder 3 is closed, and the lower end is open.

[0023] In Figure 1, a supply pipe 5 and a discharge pipe 8 are connected to the side wall 2b of the tank body 2, respectively. Inside the tank body 2, the supply pipe 5 extends horizontally, then bends and opens vertically upward inside the inner cylinder 4. This configuration ensures that the supply pipe 5 does not obstruct the rotation of the rotating shaft 10 and the lower blade 12.

[0024] The flotation separator 1 is a pressurized flotation device, and a mixture of water to be treated and pressurized water is introduced through the opening 5a of the supply pipe 5. In this case, a pressurized water supply pipe is connected to the middle of the supply pipe 5, and the pressurized water and water to be treated are mixed within the supply pipe 5. Pressurized water is produced by dissolving air under high pressure in a pressurized tank or the like.

[0025] The inner cylinder 4 is located approximately in the center of the outer cylinder 3 and is fixed to the outer cylinder 3, for example, by a frame. The inner cylinder 4 has an open upper end and has an inner cylinder tapered section 4a at its upper end that widens in diameter upwards. The shape of the inner cylinder 4 is not particularly limited, but having such an inner cylinder tapered section 4a makes it easier to disperse the water to be treated so that it spreads radially at the upper part of the outer cylinder 3. The lower end of the inner cylinder 4 is also open. Having an open lower end allows the water to be treated to flow back into the inner cylinder 4, and also allows sediment and other materials to fall downwards from the inner cylinder 4. The inner cylinder 4 may also have a closed lower end (bottomed shape).

[0026] When mixed water is introduced into the flotation separator 1, the air dissolved in the pressurized water turns into bubbles. Suspended solids in the water to be treated attach to these bubbles, forming flocculated solids that float to the surface. The water to be treated, from which the suspended solids have been removed, then descends through space A between the outer cylinder 3 and the inner cylinder 4, wraps around the lower end of the outer cylinder 3, rises between the outer cylinder 3 and the tank body 2, and is finally discharged outside the system.

[0027] In the flotation separator 1 shown in Figure 1, a flow straightening unit 6 and a flow straightening plate 7 are provided as flow straightening members to suppress the occurrence of turbulent flow in the water to be treated. The flow straightening unit 6 is located at the bottom of space A, and the flow straightening plate 7 is located at the top of space A. In particular, the flow straightening unit 6 is a flow straightening member that eliminates the non-uniformity of the downward velocity of the water to be treated by allowing the water to be treated, from which suspended solids have been removed, to pass from top to bottom.

[0028] Here, the details of the flow straightening unit will be explained based on Figure 2. Figure 2(a) is an enlarged view of the area around the flow straightening unit in Figure 1, showing a cross-sectional view. Figure 2(b) is a plan view of the flow straightening unit from above. As shown in Figures 2(a) and (b), the flow straightening unit 6 is composed of multiple frustoconical cylindrical inclined plates 6a to 6e of different diameters arranged concentrically. The inclined plate with the smallest diameter, 6a, is positioned closest to the inner diameter, and as the diameter increases, they are positioned closer to the outer diameter, with the inclined plate with the largest diameter, 6e, positioned closest to the outer diameter. These inclined plates are connected by, for example, a radially extending frame (not shown), and are integrated while maintaining a distance from each other.

[0029] The rectifier unit 6 is configured such that its constituent inclined plates 6a to 6e are arranged to decrease in diameter downwards. In other words, the larger diameter side of the inclined plates 6a to 6e is positioned upwards, and the smaller diameter side is positioned downwards. In Figure 2(a), the inner diameter of the smaller diameter side of the inclined plate 6a is smaller than the inner diameter of the inner cylinder 4. Also, the lower end of the inner cylinder 4 is positioned close to the inclined plate 6a.

[0030] As shown in Figure 2(a), the outer cylinder 3 has a tapered outer cylinder section at its lower end, which narrows in diameter downwards. This tapered outer cylinder section constitutes part of the inclined plate of the rectifier unit 6 (the outermost inclined plate 6e).

[0031] In the rectifier unit 6, the arrangement of the inclined plates is not particularly limited, but for example, as shown in Figure 2(b), they are arranged so that the spacing a, b, c, and d between adjacent inclined plates in the radial direction are approximately equal. Alternatively, the spacing between adjacent inclined plates in the radial direction may increase continuously or in stages toward the inner diameter. In this case, for example, the spacing a > spacing b > spacing c > spacing d may be.

[0032] Furthermore, in the rectifier unit 6, the inclination angles of the inclined plates 6a to 6e with respect to the vertical direction are not particularly limited, but are preferably within the range of 30° to 60°, and more preferably within the range of 30° to 50°. Figure 2 shows the inclination angles θ of the inclined plates 6a to 6e. a ~θ eare all set to 45°. Each inclination angle θ a to θ e may be angles different from each other. For example, the inclination angle of the inclined plate may be decreased continuously or stepwise toward the inner diameter side. In this case, for example, θ a < θ b < θ c < θ d < θ e may be satisfied.

[0033] The inclined plates 6a to 6e are formed of a metal plate (for example, a stainless steel plate) or a resin plate having a predetermined thickness. The same also applies to a flow straightening plate 7 described later.

[0034] Note that the configuration of the flow straightening unit is not limited to that shown in Fig. 2. For example, although the flow straightening unit 6 is configured with five inclined plates in Fig. 2, it may be configured with a larger or smaller number of inclined plates. In addition, the positional relationship between the flow straightening unit 6 and the inner cylinder 4 is not particularly limited, and for example, the flow straightening unit 6 may be provided on the lower side spaced apart from the inner cylinder 4.

[0035] Returning to Fig. 1, a flow straightening plate 7 is provided at an upper part of a space A. The flow straightening plate 7 is in the shape of a truncated cone with a larger diameter than the inner cylinder tapered portion 4a. The flow straightening plate 7 is provided so as to be located on the outer side of the inner cylinder tapered portion 4a and to have a diameter decreasing downward. The flow straightening plate 7 is fixed by a frame or the like while maintaining a gap with the outer cylinder 3 and the inner cylinder 4.

[0036] Here, the flow velocity of the upward flow generated within the inner cylinder 4 is greater in the center of the inner cylinder 4 than in the periphery, resulting in non-uniformity of the flow velocity. The water to be treated, with its high flow velocity, flows from the inner cylinder 4 towards the outer cylinder 3, and after reaching the outer cylinder 3, it tends to generate a high-velocity downward flow. In contrast, in the configuration shown in Figure 1, by providing the flow straightening plate 7, the water to be treated flowing out from the upper end of the inner cylinder 4 is diverted to either the inside (between the flow straightening plate 7 and the inner cylinder 4) or the outside (between the flow straightening plate 7 and the outer cylinder 3), thereby slowing down the flow velocity of the water to be treated at the top of the outer cylinder 3, and consequently slowing down the flow velocity of the downward flow. In other words, the velocity difference between the downward velocity near the outer cylinder 3 and the downward velocity near the inner cylinder 4 can be suppressed.

[0037] Furthermore, in Figure 1, the rectifier plate 7 is positioned such that its upper end is higher than the upper end of the inner cylinder tapered section 4a. Also, the rectifier plate 7 is positioned such that its lower end is lower than the lower end of the inner cylinder tapered section 4a. By positioning the rectifier plate 7 to accommodate the entire inner cylinder tapered section 4a in this way, it becomes easier to slow down the flow velocity of the treated water flowing out from the upper end of the inner cylinder 4.

[0038] Next, Figure 3 will be used to explain the flow of water to be treated in the flotation separator. The water to be treated and pressurized water are pre-mixed and supplied as mixed water from the supply pipe 5 into the inner cylinder 4. The mixed water supplied into the inner cylinder 4 becomes an upward flow and flows out from the upper end of the inner cylinder 4 to the upper part of the outer cylinder 3. Since the inside of the inner cylinder 4 and outer cylinder 3 is under atmospheric pressure, the air dissolved in the pressurized water becomes fine bubbles (for example, 1 μm to 5 μm), and the surface of these bubbles becomes electrostatically charged, causing suspended solids in the water to adhere to them. As a result, the aggregated flocs are separated by flotation and scraped together by the rotation of the upper blade 11.

[0039] The treated water that flows out from the upper end of the inner cylinder 4 to the top of the outer cylinder 3 is diverted so as to curve around the inside or outside of the flow straightening plate 7, thereby slowing down its flow velocity. As a result, the downward flow of the treated water descending through the space between the outer cylinder 3 and the inner cylinder 4 is also slowed down.

[0040] The treated water then flows as a downward flow through the space between the outer cylinder 3 and the inner cylinder 4, passing through the flow straightening unit 6. By passing through this flow straightening unit 6, the flow of the treated water is straightened, and the difference in downward velocity is reduced. In other words, the downward velocity near the outer cylinder 3, where the downward velocity is relatively high, becomes slower, so that the downward velocity of the treated water flowing out of the flow straightening unit 6 becomes uniform overall. As a result, the occurrence of turbulence can be suppressed, and thus the treatment capacity can be improved.

[0041] Furthermore, generally, the space B below the inner cylinder 4 has almost no flow velocity of the water to be treated and tends to become a dead space in the flotation separation process. In contrast, by providing a flow straightening unit 6 as shown in Figure 3, the water to be treated can be forcibly sent into space B, thereby improving the treatment capacity. From this viewpoint, it is preferable that the flow straightening unit 6 be provided close to the lower end of the inner cylinder 4. In Figure 3, the flow straightening unit 6 is provided such that the lower end of the inner cylinder 4 is located inside the flow straightening unit 6.

[0042] The water to be treated, after passing through the rectifier unit 6, rises through the space between the outer cylinder 3 and the tank body 2 and is discharged out of the system through the discharge pipe 8.

[0043] For example, in the case of a pressurized flotation device, the amount of fine air generated is proportional to the amount of pressurized water and the pressure of the pressurized water. Specifically, 19 mL of air dissolves in 1 L of pressurized water at 1 MPa at 20°C. Therefore, at 4 MPa, the amount of dissolved air AV (mL) = 19 × 4 Q = 76 Q, given the pressurized water volume Q. Thus, it can be seen that the processing capacity of a pressurized flotation device capable of introducing a large amount of pressurized air is proportional to the amount of pressurized water that can be supplied.

[0044] However, increasing the amount of pressurized water can cause turbulence, where the rising bubbles from the pressurized water and the rising water flow of the pressurized water can destroy the floating flocs or create areas of high and low flow velocity. When turbulence occurs, the aggregated flocs may be destroyed and broken down by turbulent agitation, and flocs in the high-speed areas of the turbulent flow may not float but be mixed into the treated water or circulating water along with the circulating water that is drawn into the pump to produce pressurized water, potentially causing poor separation in the pressurized treatment. This circulating water is the sum of the raw water supplied to the pressurized flotation system and the amount of pressurized water supplied by the pressurizing pump. The point at which this circulating water flow does not cause turbulence within the pressurized flotation system represents the maximum treatment capacity. Therefore, the amount of circulating water that causes turbulence depends on the flow velocity v (m / s) of the circulating water in the tank, the diameter D (m) of the pressurized flotation system, the viscosity μ (kgm / s) of the pressurized water, and the density ρ (kg / m³) of the circulating water. 3 If we assume that turbulence occurs when the Reynolds number (Re) exceeds 10, then we get the following equations (1) and (2). Re=ρv 2 D / μ<10···(1) v = √(10μ / ρD)···(2)

[0045] As can be seen from these equations, the flow becomes less turbulent in proportion to the diameter D, so it can be concluded that there is a proportional relationship between the diameter and the processing capacity of the pressurized flotation device. v=√(10×1 / 1 / 2)=2.2(m / s)···(3) The circulation rate can be increased up to the following conditions. The maximum flow rate of laminar flow in a cylinder with a diameter of 2m is given by equation (4) below. Q = 1 × 1 × 3.14 × 2.2 = 6.9 m 3 / s × 60s / hr = 414m 3 / hr···(4)

[0046] According to the above calculation, the maximum circulation volume is 400m 3 It can be increased up to / hr. Here, 400m 3The diameter of a pressurized flotation device with laminar flow at a rate of / hr is D = √(400 / 3.14) = 11.3 m. From this, for example, according to the flotation separation device of the present invention, even a pressurized flotation device with a diameter of 2 m can achieve a circulating flow that is almost equivalent to that of a pressurized flotation device with a diameter of 11 m, while maintaining laminar flow.

[0047] According to the present invention, for example, by equalizing the flow velocity of the downflow within the pressurized flotation device, the flow velocity of the pressurized flotation circulation volume can be equalized, allowing it to flow in a laminar state. Furthermore, by maintaining a laminar state even when the pressurized flotation circulation volume is increased, the circulating water volume can be increased, thereby improving the capacity of the pressurized flotation device.

[0048] The flotation separator of the present invention is not limited to the configuration shown in Figures 1 to 3. For example, in Figures 1 to 3, a supply pipe 5 is provided inside the inner cylinder 4 as a means of discharging the water to be treated into the tank, but the inner cylinder 4 may be omitted and the water to be treated may be discharged using only the supply pipe 5. In this configuration, the supply pipe 5 also functions as the inner cylinder.

[0049] Furthermore, while Figures 1 to 3 show a configuration in which the tank body 2 is provided on the outside of the outer cylinder 3, the tank body 2 may be omitted and the outer cylinder 3 may be used as the tank body. In this configuration, the purified treated water is discharged from the bottom of the device, so the discharge means is located below the flow straightening unit 6.

[0050] Alternatively, a flow straightening plate with multiple flow straightening holes may be provided separately, as in conventional flotation separation devices.

[0051] Furthermore, although a pressurized flotation device was used as the flotation separation device in Figures 1 to 3, the flotation separation device of the present invention is not limited to this, and can be any device that separates suspended solids in the water to be treated by attaching them to bubbles. For example, methods for generating bubbles include a swirling flow type and a static mixer type. [Industrial applicability]

[0052] The flotation separation device of the present invention can maintain a laminar flow state and has excellent processing efficiency, even when the device is miniaturized and the amount of circulating water is increased, and can therefore be widely used as a flotation separation device. [Explanation of Symbols]

[0053] 1 Flotation separation device 2 tank body 2a Lid 2b Side wall part 2c bottom 2d recess 3. Outer cylinder 4 Inner cylinder 4a Inner cylinder tapered section 5 Supply pipe 5 supply ports 6. Rectifier Unit 6a, 6b, 6c, 6d, 6e inclined plate 7 Rectifier plate 8 Discharge pipe 9 Motors 10 Rotation axis 11 Upper blade 12 Lower blade A, B space

Claims

1. A flotation separation device comprising an outer cylinder arranged vertically and an inner cylinder provided approximately in the center of the outer cylinder with an open upper end, wherein the water to be treated is discharged from the upper end of the inner cylinder, suspended solids are attached to air bubbles and separated by flotation, and the treated water from which the suspended solids have been separated is then allowed to descend into the space between the outer cylinder and the inner cylinder before being discharged outside the system, A flow straightening unit is provided at the bottom of the aforementioned space through which the water to be treated passes. This flow straightening unit is composed of multiple frustoconical cylindrical inclined plates of different diameters arranged concentrically and is positioned to narrow in diameter downwards. The flotation separation device is characterized in that the inner cylinder has an inner cylinder tapered portion at its upper end that widens upward, and a frustoconical flow straightening plate, which is larger in diameter than the inner cylinder tapered portion, is provided on the outside of the inner cylinder tapered portion and narrows in diameter downward, and the upper end of the flow straightening plate is positioned higher than the upper end of the inner cylinder tapered portion, and the narrowed lower end is positioned lower than the lower end of the inner cylinder tapered portion.

2. The flotation separation device according to claim 1, characterized in that the inclined plates in the rectifying unit are arranged such that the distances between them and other radially adjacent inclined plates are approximately equal.

3. The flotation separation device according to claim 1 or 2, characterized in that the inclination angle of the inclined plate with respect to the vertical direction is within the range of 30° to 50° in the rectification unit.

4. The flotation separation device according to claim 1 or 2, characterized in that the outer cylinder has a tapered outer cylinder portion at its lower end that is tapered downwards, and the tapered outer cylinder portion constitutes a part of the inclined plate of the rectifying unit.

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