JPH0312951B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a wastewater flotation separation method using both dispersed bubbles and precipitated bubbles, and a flotation separation device used in the method. The present invention can be applied not only to general wastewater treatment but also to flotation separation treatment of various liquids, such as sludge concentration treatment. Furthermore, the gas used in the present invention does not necessarily have to be air; for example, nitrogen-rich air (the gas remaining after oxygen is selectively extracted from air) can also be used. [Prior art] Generally used flotation separation treatment methods and devices for wastewater include (a) pressurized flotation separation methods and devices that utilize precipitated bubbles, and (b) conventional methods and devices that primarily utilize dispersed bubbles. This is a pressure flotation separation method and device. In addition, electrolytic flotation separation methods and devices, flotation separation methods and devices using aeration tubes, etc. are known, but these methods and
The device is limited to special uses. (a) Pressure flotation separation method/equipment Water and air are retained in a pressure vessel, the air is dissolved in water under pressure while exhausting excess air, and this dissolved liquid is extracted to make waste water from the flotation tank. Introduce it inside. Dissolved air becomes bubbles under atmospheric pressure, and impurities (components to be removed) in wastewater are removed.
Since the impurities precipitate and adhere to the aggregates, the impurities are floated and separated by the buoyancy of the precipitated bubbles. That is, according to this method, impurities in wastewater are separated mainly by the adhesion action of precipitated bubbles. pressure·
Although it depends on conditions such as temperature, in general, according to this method, the amount of precipitated bubbles is 2 times the normal volume of water.
~3%. Furthermore, according to this method, bubbles are deposited in both aggregated impurities and non-agglomerated impurities, so separation accuracy is high. (b) Atmospheric pressure flotation separation method and device: Introducing air into water and passing it through a static mixer to create dispersed bubbles in the water, and mixing the water containing the dispersed bubbles with wastewater,
Further, by adding a polymer flocculant, impurities are flocculated. At this time, the dispersed bubbles present in the wastewater are trapped in the coagulating impurities, and the impurities are floated and separated by the buoyancy of the dispersed bubbles. That is, according to this method, impurities in wastewater are separated mainly by the enclosing action (inclusion action) of dispersed bubbles. Generally, according to this method, the amount of dispersed bubbles is 10 to 30% of the normal volume of water, and since the amount of bubbles is larger than that in the pressure flotation method, the flotation rate is faster. Furthermore, the apparatus of this method is relatively smaller and simpler than the apparatus of the previous method. [Problems to be Solved by the Invention] According to the pressure flotation method, there are problems in that the flotation speed is slow because the amount of bubbles is relatively small, and a large flotation tank is required. In addition, a large pressurized tank and a device to control the level within the tank are required, and the piping becomes complicated, making the entire device larger, increasing the installation cost, and handling the operation and maintenance of the device. The problem is that it becomes complicated. According to the normal pressure flotation separation method, impurities that have already been aggregated by the polymer flocculant and impurities that do not (or are difficult to aggregate) by the polymer flocculant are treated by the entrapping effect of dispersed bubbles. As a result, the separation accuracy of impurities is inferior to that of the pressure flotation separation method. Furthermore, as long as dispersed bubbles are created by mechanical operations, it is inevitable that large diameter bubbles will be generated in the liquid. Such coarse bubbles (for example, about 100 μm or more) have a stronger stirring action than adhesion or entrapment action, and are thought to be one of the factors that impairs separation accuracy. [Purpose of the Invention] Based on the advantages and disadvantages of the conventional flotation separation methods and devices, the inventor of the present application has conducted various tests on each of these devices, and has found the following (a) to (c). We have come to confirm the facts shown below. (a) When flotation separation is performed using both precipitated bubbles and dispersed bubbles, the separation speed tends to increase and the separation accuracy also tends to increase. (b) The effectiveness of both bubbles differs depending on the type of wastewater and treatment target level. For example, for oil-containing wastewater from an oil refinery, it is better to increase the number of precipitated bubbles, and for wastewater from a cafeteria, it is better to increase the number of dispersed bubbles to obtain better results. (c) Removal of coarse bubbles in the dispersed bubbles improves separation accuracy. Therefore, the present invention provides a flotation separation method that can effectively treat various types of wastewater by generating dispersed bubbles and precipitated bubbles in arbitrary amounts and proportions in wastewater, and a flotation separation method that can be used in the method. The purpose is to provide an effective flotation separation device. [Means for Solving the Problems] The flotation separation method of the present invention involves pumping gas and liquid into a cyclone, and stirring and stirring the fluid within the cyclone.
The gas is dispersed and dissolved in the liquid by stagnation, and the light fluid (fluid with a small apparent specific gravity) and heavy fluid (fluid with a large apparent specific gravity) are separated by centrifugal force. The liquid containing (coarse dispersed bubbles and surplus fine dispersed bubbles) is extracted from the overflow port of the cyclone and passed through the injector, and the gas is drawn into the injector using a suction force that corresponds to the kinetic energy of the fluid passing through the injector. Further liquid is added to the fluid that is suctioned and flows out from the injector, and the liquid is returned to the cyclone, and the heavy fluid, that is, the liquid that contains arbitrary fine dispersed air bubbles and has an arbitrary proportion of gas dissolved therein, is extracted from the underflow port of the cyclone. , the wastewater is treated by introducing the fluid into a flotation separation tank to generate fine dispersed bubbles and precipitated bubbles in the wastewater in an arbitrary amount and ratio. In addition, the flotation separation device of the present invention includes a pump that pumps gas and liquid, and internally stirs and stagnates the gas and liquid supplied from the pump to disperse and dissolve the gas in the liquid, and also uses centrifugal force to disperse and dissolve the gas in the liquid. A cyclone separates a light fluid (a fluid with a small apparent specific gravity) from a heavy fluid (a fluid with a large apparent specific gravity); an injector through which a liquid containing (excess fine dispersed air bubbles) passes, sucks gas into the interior with a suction force corresponding to the kinetic energy of the passing fluid, and whose fluid outlet is connected to the suction port of the pump; and a flotation separation tank that is connected to the suction port of the pump to send liquid to the pump, and is also connected to the underflow port of the cyclone to send heavy fluid, that is, a dissolved liquid containing fine dispersed bubbles into the tank. It is characterized by [Operation] The liquid extracted from the flotation tank is supplied to the pump from the suction port together with gas. The gas is pulverized inside the pump, dispersed in the liquid, and partially dissolved in the liquid. The fluid discharged from the pump flows into a cyclone, and the fluid is stirred by rotational movement within the cyclone,
The gas further dissolves into the liquid through stirring and residence. In the cyclone, a large amount of liquid containing a large amount of undissolved gas (liquid containing coarse dispersed bubbles and a surplus of fine dispersed bubbles) is collected in the center of the cyclone by centrifugal force. The liquid containing more undissolved gas is extracted from the overflow port of the cyclone, supplied to the injector, and passes through the injector toward the outlet. At this time, a suitable amount of gas is sucked into the injector by a suction force depending on the kinetic energy of the fluid passing through the injector, and the gas is dispersed in the fluid. The fluid that has passed through the injector enters the suction port of the pump together with the liquid that has been drawn out from the flotation tank, is compressed again, and is sent to the cyclone. That is, a liquid containing a larger amount of undissolved gas is circulated between the cyclone injector and the pump, and the injector self-controls the intake air amount according to the proportion of dispersed bubbles contained in this fluid. And on the other hand,
The dissolved liquid in the cyclone containing fine dispersed air bubbles is extracted from the underflow port and introduced into the wastewater in the flotation tank. The gas dissolved in the liquid becomes precipitated bubbles in the wastewater under atmospheric pressure, and due to the entrapment effect of the dispersed bubbles and the adhesion effect of the precipitated bubbles,
Impurities in wastewater are effectively floated and separated in a short time and with high precision. [Example] An example of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic structural diagram showing a flotation separation device 1 according to this embodiment. 2 in the figure is a conditioning device to which raw wastewater is supplied, and this device 2 is provided with a stirrer 3. Raw wastewater is conditioned device 2
The wastewater (water to be treated) enters the pipe P1 from the inlet 4 and is sent to the auxiliary tank 6a of the flotation tank 6 via the T pipe 5. It is composed of A rotary vane type scum skimmer 7 is provided at the upper part of the flotation separation tank 6, so that impurities floating on the surface of the wastewater W stored in the tank can be scraped out of the tank. Further, an outlet 8 of the treated water is connected and communicated with the lower part of the flotation separation tank 6 via a pipe P2. A pipe P3 is connected to the bottom of the funnel-shaped flotation tank 6, and the pipe P3 is connected to the suction port 11 of the pump 10 via a T pipe 9.
are connected and communicated. Therefore, the treated water in the flotation tank 6 is supplied to the pump 10. Next, the pump 10 is provided to disperse and dissolve air as a gas into water as a liquid, and to pump these fluids to a cyclone 22, which will be described later. The pump 10 may be a normal centrifugal pump (for example, a single-side suction horizontal non-self-contained pump with a simple, inexpensive, and easy-to-handle structure), but in general, in a normal centrifugal pump, the proportion of gas in the inflowing fluid is small. If it becomes too large, vibrations, abnormal noises, abnormal wear of the rotating blades, etc. may occur, and other problems may occur, such as the inability to discharge fluid or the fluid being discharged intermittently. The inventors of the present invention believe that the cause of such inconvenience lies in the shape of the fluid passage in the impeller section, and further confirmed that the cause is that the cross-sectional area of the fluid passage is larger on the outlet side than on the inlet side. Therefore, in this embodiment, as will be described later, a pump having a structure that can pump more gas together with liquid is used to further enhance the effectiveness of the entire apparatus. Reference numeral 12 shown in FIG. 2a is an impeller body composed of a main plate 14 having a boss 14a to which a drive shaft 13 is attached, and a plurality of blades 15 provided on one side of the main plate 14. . The blades 15 of the impeller body 12 have holes 16a in the center.
A disk-shaped side plate 16 having a shape formed thereon is fixed thereto, and constitutes an impeller portion 17. As shown in FIG. 2a, the blades 15 have a claw-shaped cross-sectional shape curved into an arc, and each blade 15, the side surface of the main plate 14, and the inner surface of the side plate 16 form a plurality of blades. A fluid passageway 18 is defined. Unlike the fluid passage in a normal centrifugal pump, this fluid passage 18
is an elliptical inlet 19 as shown in FIG. 2b.
The side cross-sectional area is large, and the cross-sectional area on the elliptical outlet 20 side is smaller, and its wall surface has a smooth shape with no corners. However, depending on cost and other considerations, the cross-sectional shape of the fluid passage 18 may be
It may also have a rectangular corner. In addition, both cross-sectional areas are determined by the fluid pressure at the outlet 20 and the fluid pressure at the outlet 20 so that the apparent flow rate of the fluid in the fluid passage 18 (the value obtained by dividing the apparent volume of fluid flowing within a certain period of time by that time) is constant. It is set based on the mixing ratio of gas and liquid. For example, when trying to mix and transfer 6 m ³ /h of water and 2 m ³ /h of air, if the pressure of the fluid at the outlet 20 is 5 Kgf/cm ² , the volume of the gas will be compressed to about 1/5; Cross-sectional area A on the 19 side and cross-sectional area on the exit 20 side
A' can be determined by the following equation. 6+2/A=6+0.4/A' Next, the discharge port 21 of the pump 10 is connected and communicated with a cyclone 22. cyclone 22
The fluid supplied from the pump 10 is stirred and retained under pressure to dissolve and disperse gas in the liquid, and centrifugal force is used to separate light fluid (fluid with small apparent specific gravity) and heavy fluid (fluid with small apparent specific gravity). As shown in FIG. 3a, this cyclone 22 is a fluid tank for separating large fluids (large fluids), and is formed into a substantially truncated conical shape. A pipe P4 led from the discharge port 21 of the pump 10 is tangentially connected to the upper side of the cyclone 22 via a pressure gauge G1. Further, a pipe P5 is connected to and communicates with a circulating fluid outlet 23 as an overflow port provided in the center of the upper half. When the cyclone 22 is installed vertically as in this embodiment, the circulating fluid outlet 2
It is preferable that the pipe P5 connected to the cyclone 3 not protrude into the inside of the cyclone 22. A pipe P6 is connected to a liquid outlet 24 which is provided at the lower end of the cyclone 22 and serves as an underflow port through which the solution is discharged. The pipe P6 is provided with a valve V1 and a polymer flocculant inlet 25, and communicates with the T-pipe 5 via a static mixer 26. Therefore, the solution from the cyclone 22 joins the water to be treated through the T pipe 5 and is led into the auxiliary tank 6a of the flotation tank 6. The cyclone 22 of this embodiment is installed vertically, but when the cyclone 28 having the central axis 27 as shown in FIG. It's good to let them do it. Next, the circulating fluid outlet 2 of the cyclone 22
3 is connected to the inlet 30 of the injector 29 via a flowmeter G2 and a valve V2. As shown in FIG. 4, the injector 29 is a pipe-shaped device with a passage in the center through which the fluid passes, and has a tapered shape in which the inner diameter is narrowed from the inlet 30 to the center where the throttle hole 31 is located. It is formed in a tapered shape in which the inner diameter increases from the central part to the outlet 32. And on the outer peripheral surface of the center part, there is a first aperture hole 31.
A suction port 33 is formed in communication with the suction port 33, and gas is sucked through the suction port 33 by the kinetic energy of the fluid passing from the inflow port 30 toward the outflow port 32. Also, a check valve 34 is provided inside the suction port 33, and the inlet 3
The fluid flowing from the outlet 32 toward the outlet 32 is prevented from being discharged from the suction port 33 to the outside. In addition, a disk-shaped twisting blade 35 is provided at the inlet port 30 of the injector 29.
is rotatably provided to stabilize the gas suction force and to effectively atomize the gas sucked into the injector 29. In addition, instead of such a disk-shaped twisting blade 35, a propeller-shaped blade with less pressure loss may be provided. Next, a pipe P7 is connected to the suction port 33 of the injector 29. A valve V3 and a flow meter G3 are connected to the pipe P7, and the gas inlet 33 is open to the atmosphere at a predetermined pressure.
Further, the pipe P8 connected to the outlet 32 of the injector 29 is inserted into the T-pipe 9 connected to the suction port 11 of the pump 10 from the other open end. Therefore, the fluid extracted from the circulating fluid outlet 23 of the cyclone 22 takes in air through the injector 29, joins with the water in the flotation tank 6 through the T-pipe 9, and is sucked into the pump 10. ing. Next, a method for flotation separation of waste liquid using the apparatus configured as described above will be described. The pump 10 is driven by a drive means (not shown), and air and water in the flotation separation tank 6 are sucked into the pump 10. The liquid and gas sucked into the impeller portion 17 are pressurized while moving through the fluid passage 18 having a smooth shape. The fluid passage 18 of the impeller part 17 in the pump 10 of this embodiment has a large cross-sectional area on the inlet 19 side through which the uncompressed fluid passes, and a small cross-sectional area on the outlet 20 side through which the compressed fluid passes. . Therefore, when a liquid and a gas, which is a compressible fluid, are pumped together, the inlet 19 in the fluid passage 18
Since the apparent flow velocity of the fluid (the value obtained by dividing the apparent volume of the fluid flowing within a certain period of time by that time) from the to the outlet 20 is constant, there are no regions with different pressures within the fluid passage 18, and the fluid passage 18
No inconveniences such as the generation of harmful vortices will occur. In particular, in this embodiment, the fluid passage 18
Since the wall surface has a smooth shape with no corners, the resistance between the wall surface and the fluid is uniform in all parts, and fluid vortices that can wear the wall surface occur in specific parts. There's no fear. In this way, the gas and liquid sucked into the impeller section 17 are smoothly transferred at a constant flow rate without creating a flow inside the smooth-shaped fluid passage 18, so even when a considerable amount of gas is pumped together with the liquid, During operation of the pump 10, troubles such as abnormal noises and vibrations do not occur, and the wall surface of the fluid passage 18 does not wear abnormally. Then, in the impeller section 17, the sucked gas is pressurized and pulverized into fine pieces, dispersed and mixed in the liquid, and a part of the gas is dissolved in the liquid. The fluid discharged from the pump 10 is transferred to the cyclone 22
The fluid enters the cyclone 22 and is stirred while rotating vigorously under pressure, and the gas is further dissolved into the liquid by stirring and retention. In the cyclone 22, the light fluid, that is, the liquid containing more undissolved bubble-like gas, gathers in the center of the cyclone 22 due to centrifugal force. Additionally, gases that have become difficult to dissolve due to their association and increase in volume, and gases that are coarse from the beginning, also gather in the center.
That is, in the cyclone 22, centrifugal force separates gas and liquid and separates gas and gas (separation of coarse and fine bubbles).
are being done at the same time. On the other hand, heavy fluid, that is, a liquid containing a certain amount of fine dispersed bubbles and dissolved gas (dissolved liquid), moves to the lower half of the cyclone 22 while rotating, and passes through the liquid outlet (underflow port) 24. It is sent to valve V1. In this case, the amount of solution coming out of the liquid outlet 24 is kept constant by appropriately adjusting the opening degree of the valve V1, so the pressure in the system of this device including the cyclone 22 is kept constant. It's dripping. Then, the solution containing fine dispersed bubbles that has passed through the valve V1 is transferred to the inlet 25.
After a polymer flocculant is added thereto, it is stirred in a static mixer 26, and is combined with wastewater (pretreated) in a T pipe 5 and sent into an auxiliary tank 6a of a flotation tank 6. Since the flotation separation tank 6 is open to atmospheric pressure, the gas dissolved in the liquid becomes precipitated bubbles in the wastewater under atmospheric pressure, adheres to impurities in the wastewater, and floats and separates them. On the other hand, since dispersed air bubbles are trapped in the impurities aggregated by the polymer flocculant, these impurities are also floated and separated. As described above, according to the method of this embodiment, the adhering action of the precipitated bubbles and the enclosing action of the dispersed bubbles have a synergistic effect, and impurities in wastewater are efficiently floated and separated in a short time with high accuracy. The floating impurities are scraped out of the tank by the scum skimmer 7, and the treated water passes through the pipe P2 and is discharged from the outlet 8 to a predetermined position outside. Next, the water containing more undissolved air bubbles is
The circulating fluid is extracted from the circulating fluid outlet 23 (overflow port), supplied to the inlet 30 of the injector 29, and passes through the injector 29 toward the outlet 32. At this time, air is sucked into the injector 29 from the suction port 33 by the kinetic energy of the passing fluid. The suction force of air varies depending on the kinetic energy of the passing fluid, that is, the amount of bubbles contained in the fluid. For example, the circulating fluid outlet 23
If the fluid extracted contains many bubbles, the kinetic energy of the fluid is small, so the injector 2
The amount of air sucked into 9 is reduced. Conversely, if the fluid contains almost no air, a large amount of air will be sucked into the injector 29 by a strong suction force corresponding to its kinetic energy. In this way, in the device 1 of this embodiment, the amount of gas suction is self-controlled. The air sucked in by the injector 29 is dispersed in the liquid together with the undissolved gas sent from the cyclone 22, and is atomized in the injector 29 and dispersed and mixed in the liquid. Further, in this embodiment, since the injector 29 is provided with the twisted blades 35, the gas suction state is stable. Next, the fluid that has passed through the injector 29 is sent into the T-pipe 9 via the pipe P8. Then, this fluid joins the water sent from the flotation tank 6 and is sucked into the pump 10. As described above, the liquid sent from the cyclone 22 to the flotation separation tank 6 contains a predetermined amount of fine dispersed air bubbles, and also dissolves air that becomes precipitated air bubbles under atmospheric pressure. By appropriately adjusting the amount and ratio of dispersed bubbles and precipitated bubbles in the wastewater W in the flotation tank 6 according to the properties of the wastewater W to be flotated, highly accurate and efficient flotation can be carried out in various ways. This can be done for waste liquid. In the embodiment described above, the amount of dispersed bubbles can be increased or decreased by adjusting the amount of suction air of the cyclone 29 by operating the valve V3. In addition, the saturated dissolution amount of air in water is determined by the pressure, and the residence time until reaching saturation in the cyclone 22 is determined by the equipment system, so at the maximum discharge pressure, the pump 1
The discharge amount of the cyclone 22 may be determined by the residence time. Since the discharge pressure of the pump 10 can be lowered by increasing the amount of circulating water, the amount of precipitated bubbles can also be adjusted. As described above, in this embodiment, an appropriate amount of water is extracted from the flotation tank 6 and supplied into the system, and a part of the fluid containing a larger amount of undissolved gas is separated by the cyclone 22 by centrifugal force. While circulating this gas within the system, the injector 29 self-controls the amount of intake air to efficiently disperse and disperse the gas into the liquid.
It is dissolved. That is, in the device 1 of this embodiment, since the fluid is circulated, there are many chances of contact between gas and liquid, and since the gas is repeatedly atomized in various places, the contact area of gas and liquid is large, so that the water in the air is The dispersion and dissolution of these substances is extremely efficient. Then, the solution containing dispersed bubbles is blown out from the cyclone 22 and returned to the flotation separation tank 6.
Using fine dispersed bubbles and precipitated bubbles, flotation separation of wastewater is carried out with high precision and in a short time. Next, the results of testing the flotation and separation device 1 will be explained using a specific example. 3.7〓×2900rpm
A conventional centrifugal pump has a fluid passage 1 as described above.
Attach the impeller part 17 having the number 8. The cyclone 22 has a truncated cone shape with a diameter of 250 x 200 mm and a height of 130 mm.The injector 29 has an inner diameter of about 10 mm at the entrance and exit, a total length of about 50 mm, and an inner diameter of the throttle hole 31 of about 3 mm. I used the one from It has been experimentally confirmed that the injector 29 has an inflow pressure of 4.0 Kgf/cm ² and an inflow rate of 1/min. Now, the waste liquid to be treated here is hotel chusuke waste liquid (waste liquid generated when chusuke is crushed and dehydrated).
The test was conducted using air as the gas and varying the amount of suction air. The results are shown in Table 1 as Example 1. Also, Example 2 shown in Table 1
The data of 6 to 6 were obtained by setting the waste water to zero and adjusting the flow rate, discharge pressure, etc. of the pump by operating each valve. For comparison, the results obtained using the conventional apparatus under almost the same conditions are shown in Tables 2 and 3 together with Example 1. In Tables 2 and 3, Comparative Example A is an apparatus that mainly uses dispersed bubbles as explained in the [Prior Art] section, and Comparative Example B is an apparatus that mainly uses precipitated bubbles as explained in the [Prior Art] section. This is the device used.

【table】

【table】

[Table] As shown in Examples 2 to 6 in Table 1, according to the apparatus and method of this example, dispersed bubbles and precipitated bubbles can be obtained in arbitrary amounts and ratios. Therefore, flotation separation treatment can be carried out in accordance with the properties of the wastewater to be treated. As can be seen from Table 3, in this example, the residence time of the fluid in the flotation tank was 12 minutes, which is the same as in Comparative Example A. However, from the analysis values of the treated water shown in Table 2, the flotation separation accuracy was Example 1 is higher than Comparative Example A. Although Comparative Example B requires a considerably longer residence time than Example 1, the flotation separation accuracy is considerably inferior to that of Example 1 based on the analytical values. As described above, according to the present example, it was confirmed that the flotation separation rate was considerably high and the accuracy was very excellent, and that effective flotation separation treatment depending on the type of waste liquid could be performed efficiently. [Effect of the invention] According to the flotation separation method and device according to the present invention,
Fine dispersion bubbles and precipitated bubbles can be generated in the waste liquid in the flotation tank in arbitrary amounts and ratios, so using a small and simple device, it can be used with high precision for various types of waste liquid. This has the effect that good flotation separation processing can be carried out efficiently.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the device according to the present invention, FIG. FIG. 3a is a plan view and a front view of the cyclone in the same embodiment,
FIG. 4b is a diagram showing a horizontally installed cyclone, and FIG. 4 is a sectional view of the injector in the same embodiment. 1...Flotation separation device, 6...Flotation separation tank, 10
... pump, 11 ... suction port, 22 ... cyclone, 23 ... circulating fluid outlet as overflow port, 24 ... liquid outlet as underflow port, 28
...Cyclone, 29...Injector, 32...
Injector outlet, W...waste water.

Claims (1)

[Claims] 1 Gas and liquid are forced into a cyclone, the fluid is stirred and retained in the cyclone, and the gas is dispersed and dissolved in the liquid. The light fluid, that is, the liquid containing excess gas (coarse dispersed bubbles and surplus fine dispersed bubbles), is extracted from the overflow port of the cyclone and placed in the injector. The gas is sucked into the injector with a suction force that corresponds to the kinetic energy of the fluid passing through the injector, and liquid is added to the fluid flowing out from the injector and returned to the cyclone. A liquid containing finely dispersed bubbles and a desired proportion of gas dissolved therein is extracted from the underflow port of the cyclone, and the fluid is introduced into a flotation tank to produce finely dispersed bubbles and precipitated bubbles in a desired amount and proportion. A flotation separation method characterized by treating wastewater by generating in the wastewater. 2 A pump that pumps gas and liquid, and the gas and liquid supplied from the pump are internally stirred and retained to disperse and dissolve the gas in the liquid, and centrifugal force is used to disperse and dissolve light fluid (low apparent specific gravity). fluid)
and a cyclone that separates heavy fluid (fluid with large apparent specific gravity) from the cyclone, and a light fluid extracted from the overflow port of the cyclone, that is, a liquid containing excess gas (coarse dispersed bubbles and surplus fine dispersed bubbles). passes through and sucks gas into the interior with a suction force corresponding to the kinetic energy of the passing fluid, and an injector whose fluid outlet is connected to the suction port of the pump, and an injector whose fluid outlet is connected to the suction port of the pump and is connected to the pump. A flotation separation device characterized by comprising a flotation separation tank that sends a liquid and is communicated with the underflow port of the cyclone to send a heavy fluid, that is, a solution containing fine dispersed bubbles into the tank.