JPS58180250A - Apparatus for selective floatation of substance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Flotation is an ancient process in which bubbles of gas are introduced into a slurry or liquid mixture with or without a flotation agent to separate selected solids. Alternatively, a liquid substance adheres to the gas bubbles and rises to the surface as bubbles.

The agglomerated foam of the selected substance is skimmed from the surface of the slurry or liquid mixture or allowed to spill out. Material that does not float is usually removed as a stream called ``dross.''

Flotation has been used to separate and flocculate a wide variety of materials, such as maple ore and other minerals, coal, grain and flour, pigmented paper pulp, oil, and sewage slag. Flotation is a phenomenon relating to the surface properties of the material to be separated and/or flocculated, in order to selectively increase or decrease flotation, to generate foam, and/or to peptize the mineral surface. Usually chemicals are added.

Two basic flotation processes are used. One process is commonly referred to as dispersive air flotation, in which air is dispersed into a slurry or mixture or introduced under a rapidly rotating impeller. Another type of process, known as dissolved air flotation, is quite useful in flocculating solids and other organic materials in sewage sludge. Air or other gases are dissolved in the slurry in a first chamber operated at a superatmospheric pressure, typically 20 to 80 psig.

In the second chamber, operating at atmospheric or subatmospheric pressure, dissolved gases are liberated by reduced pressure to form bubbles, which carry the selected substances upwards. Both the air (or other gas) and the slurry or mixture must be pressurized.

+1 in dispersed air flotation. Strong stirring is necessary to generate the necessary small bubbles.

Dissolved air flotation requires vigorous stirring in a chamber under EE forces in order to dissolve the gas into a slurry or mixture. In addition, there is energy in the Bopp action that is spent compressing both gas and liquid.

It can be seen that the required energy is high in both cases. Furthermore, control of the five-foam dogfish is extremely limited, making the flotation process inefficient.

No. 3,992,491 and an improvement thereof is shown in US Pat. No. 4,228,112.

It has been found that rotating gas diffusers useful for oxygen treatment of wastewater accomplish flotation beneficially.

The present invention relates to a flotation machine for selectively flotating substances from a liquid, the apparatus having a generally square, circular or other shaped bottom and generally vertical side walls, and having a lower agitation section and an upper agitation section. a flotation chamber having a foam collection section;

It has a hollow shaft and is immersed in the liquid, and is 0.05
a rotatably actuated diffuser adapted to introduce into said liquid a gas stream in the form of bubbles with a controllable nascent diameter from less than a millimeter to more than 10 millimeters; and for injecting gas through the diffuser. With means.

Raw materials to be separated 1. A stage for introducing blowing agents and other chemicals into the chamber, and for removing and collecting the foam of buoyant material and the dregs of non-floating material. and means for.

The present invention will be described in detail below with reference to the drawings.

The present invention includes a flotation chamber, a rotary actuated diffuser, a device for injecting gas through the diffuser, a means for controlling bubble size, and a system for introducing raw materials, reagents, and blowing agents, recovering the product, and chewing the dross. Except.

The present invention relates to a flotation machine including means for normally operating a flotation chamber.

As shown in Figures 1-6, the flotation chamber consists of a square, circular or rectangular tank 1 with a flat bottom 2 and generally vertical side walls. The side walls may have a unique shape. One such shape is shown in FIGS. 1 and 2. This shape has a horizontal bunkle 3 with a curved surface 4 at the bottom and an outwardly tapered surface at the top. Horizontal baffles roughly divide the flotation chamber into a lower stirring section 6 and an upper stationary foam collection section 7.

In order to prevent the contents of the flotation chamber from swirling, a vertical panfur 8 is provided between the floor 2 of the chamber and a horizontal panfur 30, if necessary. In addition, if necessary, an insertion member 9 with a long radius is provided at a corner of the chamber to create a smooth corner instead of a gun angle. The bottom 2 of the chamber may be provided with a recess 10 for accommodating a rotating diffuser (not shown).
may be located directly above the floor part 2.

Water or other liquid is introduced under the disc-shaped member through the passageway 10a. It may also be possible to prevent solid material from collecting under the diffuser, reducing the energy required to rotate the diffuser.

Another possible shape of the side walls is shown in FIG. In this particular form, a side wall 11 surrounds the stirring section 12 and a foam collecting section 13 of increased cross-sectional area is provided with a wall 14.

The foam overflows via the foam paddle 15.

Other shapes of sidewalls may also be used.

In FIG. 6, the gas diffusion device includes a rotating disk-like member or disk 16 having a perforated diffusion member 16a through which gas is diffused into the liquid in the chamber. A stirring blade 16b may be attached to the top and/or bottom surface of the disk 16 to increase the stirring effect.

Gas is supplied to the disk 16 from a gas source via a rotating seal 17 and a hollow shaft 18. In this example. The disk 16 is fixed to a shaft 18, and this mechanism is connected to a motor 19.
is rotated by the drive device 19a.

The rotating diffuser 16 also has an axis 1 passing through the floor of the chamber.
8 may be driven from below. The disc 16 may be placed in a recess in the floor of the chamber.

For most practical flotation effects, a pan flute is placed in the stirring section to reduce the swirling motion in the chamber and to dissipate the energy of the gas-liquid flow towards which the rotating diffuser produces. Is required.

The novel panful design shown in Figures 4-7 changes the flow direction one or more times so that the final flow direction is close to vertical but different from the direction of rotation of the rotating diffuser. to achieve the required operation. For clarity of illustration, the differential user, hollow shaft, and other parts of the flotation machine have been omitted from these figures.

One embodiment of a panful that achieves the desired energy consumption is shown in FIGS. 4 and 5. The "chevron" of banflu 2,1 forces a single change in flow direction. Adequacy of liquid and gas flow is achieved by varying the length/width and angle of the panful.

In this baffle shape, the upper panfle member 21a
and the lower panful member 2lb are each 2lb with respect to the horizontal plane.
They are arranged at angles 1c and 21d and connected at 21e. Baffles may be placed on all side walls as shown in FIGS. 4 and 5.

Alternatively, it may be arranged only on two side walls. A rotating diffuser located near the bottom of the flotation chamber creates radial and upward movement of gas and liquid. A properly designed baffle creates a completely stationary surface in the upper foam collection area over a wide range of buoyant particle sizes and diffuser-generated agitation energies.

In an alternative baffle configuration 31 shown in FIGS. 6 and 7, the angled panfurs are in row 31a.

31b and 31C are arranged. Two to five rows can be used, but two or six rows are preferred. Adjacent rows of baffles are attached to the sidewalls at different angles to redirect gas-liquid flow and dissipate vertically directed forces. Buckles can be placed, for example, on two or four side walls of a rectangular flotation chamber, or on any part of the periphery of a circular flotation chamber.

The baffle arrangement of Figures 6 and 7 forces two changes in flow direction. In this configuration, the spaces between the baffles allow some of the liquid that would otherwise hit the panfle to be bypassed, allowing adjustment of the amount of energy consumed.

As shown in all of FIGS. 4-7, the foam collection section of the flotation chamber may have sloped side walls and be configured to accommodate foam scrapers and gutters, such as vanes 15. desirable.

It is necessary to have a continuous flow of water into the flotation chamber so that the surface level of the liquid is maintained as the floated material leaves the car outlet weir.

Another unique feature of the flotation chamber of the embodiment of the present invention is 1.
A small stream of water is introduced under the rotating diffuser, which reduces the accumulation of solid materials under the rotating diffuser, cleans the water in the bearing area, and reduces power sensitivity. Also, any fluidizing agent, liquid or gas, may be used, including flotation agents.

As shown in Figure 3, the single rotation actuation diffuser (RAD)
) consists of a thin disc with a rotating seal, a drive, a hollow shaft, and a stirring blade and a diffusion device through which the gas enters the flotation chamber. The outside of the diffuser has a flat or preferably tapered edge, which provides a surface for the passage of very fine bubbles to continue laminar flow into the liquid without coalescence. Microscopic bubbles are generated by the shearing action of the liquid on the surface of the diffuser as the diffuser rotates. The speed of rotation is critical to the production of very fine bubbles, and by varying the speed of rotation and/or by varying the speed of airflow through the perforated device, the size of the bubbles can be varied. Also, the porosity of the device and the total surface area of the device can be controlled to obtain the desired bubble size.

Although the rotating disc-like member can be powered by compressed gas to rotate, in the preferred embodiment a rotatable hollow shaft is attached to the diffuser disc to rotate it. Such an embodiment is shown in FIGS. 8 and 9.

In the device 20 shown in FIGS. 8 and 9, the rotatably operated diffuser is mounted perpendicularly to the hollow shaft forming the main supply path for the gas introduced into the liquid and to the rotation axis of the shaft 260.
At least one gas plenum 7o is operatively connected to said main supply channel, and at least one wall of said plenum is perforated so that the gas passes through said wall to the outer surface of the disc-shaped member. Therefore, when gas is introduced into said main supply channel while the gas diffuser is rotating about its two axes while submerged in liquid, the gas enters the gas plenum 7o. and exit through said perforated wall thereof, nascent gas bubbles form on the surface of said disc-shaped member, and this nascent bubble causes the disc member 22 to pass through said perforated wall. A disk-shaped member 22 that, when rotated in a liquid, is sheared by the viscous shearing force exerted by the liquid to form fine gas bubbles;
This minimizes the coalescence of said fine shear bubbles as a result of turbulence in the jet and the path around the rotating disc-like member caused by the shear originating from the edge 72 of the 2 and spiraling outward from this edge. the disc-like member having a ratio of a total diameter of the disc-like member to its maximum thickness in the gas diffusion portion occupied by the gas brinum of at least about 10:1.

It is desirable that both the earthen wall and the lower wall of the gas plenum be perforated.

The ratio of the gas diffusion portion occupied by the plenum of the total diameter of the disk to the maximum thickness of the disk is at least about 10=1. Good results are obtained when this ratio is at least about 48:1, and even better results when it is less (ratio σ of at least about 64=1). Further, good results can be obtained when the ratio is at least about 128:1. A desirable value for this ratio is at least about 256:1.

In FIG. 8, the hollow shaft 26 is rotated by a motor 60 via a drive 28. In FIG. Gas is introduced via a rotary seal 49. If necessary, a sleeve 32 equipped with a helical flotation screw 40 may be used to recycle foam near the shaft to the stirring section.

The disk of FIG. 9 can have top and bottom surfaces that are substantially parallel to each other over their entire area.

Also, the upper and lower surfaces are substantially parallel to each other, but the cross-section of the disk may taper to a reduced thickness at the periphery only at the outer edge portion 72 of the disk.

The disk of FIG. 9 has an upper surface and a lower surface that are substantially parallel to each other over the entire area. The cross-section of the disk may be tapered to reduce the thickness at the periphery.

In yet another embodiment, agitation blades 42 and/or 44 are mounted on the top and/or bottom surfaces of disk 22 to increase the agitation energy exerted by the rotating diffuser and to increase the agitation energy in the perforated walls of the gas plenum. The aim is to reduce the size of the bubbles by increasing the shear rate.

Other examples of the stirring blade of the present invention are shown in Nos. 10 and 11.
As shown in the figure. A straight radial stirring blade 25 is shown in these figures. These may be provided on one or both sides of the disk 220.

These blades may be curved.

FIG. 11 shows a disk 22 having substantially parallel surfaces over its entire surface area.

12th~. FIG. 14 shows another embodiment with a tapered outer edge portion 39. These embodiments are preferred.

The disk of Figure 14 is placed in a recess in the bottom of the flotation chamber, with its top surface being substantially flush with the bottom of the flotation chamber.

In each of these embodiments, the diffuser 24 can be provided on the upper surface, or on the upper and/or lower surface.

There are many types of devices for collecting and removing floating bubbles from the flotation chamber. One shape shown in Figures 6-7 is
It includes a movable vane 24 attached to one or more side walls of the flotation chamber. This serves to cause the bubbles to overflow into the weir 24.

Yet another embodiment is shown in FIG. Here the groove is located approximately in the center of the foam collection section. This may surround the axis of the rotationally actuated diffuser.

Rotatably actuated diffuser 22 is further defined as follows. a gas inlet, at least one gas plenum operatively connected to the inlet, and at least one gas plenum having a perforated wall through which gas passes through the disk. It is possible to come out to the outer surface of the shaped member,
therefore.

When gas is introduced into said gas intake while the gas diffuser is rotating about its axis while submerged in liquid, gas flows into said plenum and into said perforated Nascent gas bubbles are formed on the surface of said disk-like member which escapes through the wall, and when the disk member rotates in said liquid, the viscosity exerted by the liquid increases. Sheared by shear forces to form fine gas bubbles. The above-mentioned fine particles occur as a result of turbulence in the jet between the disc-shaped member and the path around the disc member for one revolution caused by the vortices arising from the edge of the disc member and the helix outwardly from this edge. To minimize coalescence of shear bubbles, the ratio of the total diameter of the disc-shaped member to its maximum thickness in the gas diffusion portion of the gas plenum is small (approximately 10:1). Means is provided including a disc-shaped member.

The reason why the relationship between the diameter of the disk and the thickness of the disk in the gas diffusion area is so important is believed to be due to the following fact. That is, the degree of coalescence that occurs due to large vortices being generated at the edge of a single rotation disk for some reason.

It is many times thicker than the coalescence that would normally be expected from the more typical disturbances that exist under other conditions. The rapidly rotating vortex causes a drag of bubbles carried in the wake of the vortex, and then adjacent bubbles at the center of the vortex violently collide and coalesce, which is much larger than expected. It happens with speed.

In the normal disturbances that exist under other conditions.

Perhaps 6 to 12 microscopic bubbles will be combined at a time, but the resulting larger bubble volume will be large enough to defeat the purpose of achieving rapid rates of gas decomposition. However, the coalescence of fine bubbles that occurs at the velocity of the gas flow in the vortices created at the edges of the rotating disk completely defeats the purpose of retaining a large number of extremely fine bubbles to produce high decomposition rates. Therefore, tests have shown that typically thousands of shear bubbles (
Numbers on the order of six times the size of the number of inclined bubbles that coalesce under normal conditions) are single in the vortices in the track/jet emanating from the disk at high gas flow rates. coalesce into bubbles.

And this, of course, has a significant influence on the volume of the resulting coalescing bubbles.

The critical relationship between extremely thin disks and the effective formation and retention of the fine gas bubbles described above is believed to be due to several factors:

1. “Turbule” by Paul Cooper
nt BoundaryLayer on a
Rotating Disk Calculate
d with an Effective Velo
”, page 259, Figure 4.

and AIAA Journal, Vol. 9 (197
1), as shown on pages 255-261,
The thickness of the boundary layer formed on the upper and lower surfaces of the rotating disk can be expressed with a reasonable degree of accuracy by the following equation.

δ” 0.26 DRe-0125 where δ = boundary layer σ) thickness, D = overall diameter of the disk, and Re = Reynolds number of the particular equipment and fluid involved.

2. Reynolds number can be expressed by the following formula.

Re = wD2/4 v where 1w = rotational speed of the disc, D = overall diameter of the rotating disc, and V = kinematic viscosity of the liquid in which the disc is rotating.

6. Substituting this equation for the Reynolds number into the above equation 1.0 gives the following equation.

v 4, disk diameters and rotational speeds of current practical interest in the foam flotation field are approximately 16 inch diameter disks with rotational speeds of 60 Or, p, m.

A disk approximately 10 feet in diameter with a rotational speed of 5
Or, p, m, spans. The Reynolds number factor (wD2/4) in the denominator of the equation for determining the boundary layer thickness given above is approximately 6 for a 20-inch disk at each of the rotational speeds shown above. , varies from about 17 for a 4 to 10 foot disk.

5. Since the Reynolds number to the power of 0.125 remains essentially constant as the overall diameter and rotational speed of the rotating disk change, the The thickness of the boundary layer flow in a rotating disk rotated at the optimum speed can be approximately expressed as a constant multiple of the disk diameter.

δ=KD 6(a) The amount of bubble coalescence that occurs in the vortices at the edge of a rotating disk gas diffuser as the bubbles are entrained in these vortices. (b) This velocity is, in turn, approximately proportional to the pressure difference between the inside and outside of each individual vortex, and (a boundary layer of the thickness of the disk in the Cl gas diffusion region) to the thickness (d/8)
is believed to control the pressure differential. Therefore 5
The smallest possible value of the ratio (d/8) of the thickness of the disk in the gas diffusion region to the boundary layer σ) thickness should be sought.

7 5 above. It would follow from the relationship shown in that the smallest possible value of the ratio of the maximum thickness of the disk in the gas diffusion section to the overall diameter of the disk (d/D) should also be found. . Conversely, a ratio of the disk diameter to the maximum disk thickness in the gas diffusion section (D/d) as large as possible would be desirable. And this is consistent with the findings already mentioned above, namely that very satisfactory bubble shear results are obtained for rotating gas diffusers with a ratio of disk diameter to maximum disk thickness in the gas diffusion section of about 1o:1, and about It is confirmed that higher ratios up to 256:1, or even higher, produce the best results.

EXAMPLE 1 A coarse phosphate ore consisting of the following components: 75 bars/t -5 to +150 mesh; 25 percent -20 to +65 mesh was separated in a small-scale flotation apparatus of the present invention. A 16 inch diameter rotatably actuated diffuser-disc was mounted in a flotation chamber with a panfur measuring 18 inches wide, 18 inches deep, and 16 inches high. The effect of varying disk speed and airflow velocity on bone lime phosphate (BPL) flotation and recovery was determined. The result shown below is 3
The highest phosphate recovery was shown at an air flow rate of 156 cubic feet per hour (cfh) at 0.00 rpm.

□ Concentrate □ F (AD speed Air flow Floating degree BPL Recovery BPL
Ro00 31 70.4 Bo
, 0ro 00 9ro 69.5 86
．． 9no, 156 68.4 92
．． 5375 Ro1 67.4 81.
3ro 75 156 64.8 79
．． 1440 9ro 64.8 72
．． 5440 156 65, Q 72
．． 5 Example 2 Using the same phosphate ore and equipment as in Example 1, the effect of a stirring blade Q) mounted on a rotatably actuated disc was studied. The results for this particular ore are that by reducing HAD speed and/or using stirring blades, BPL
showed a decline in both quality and tithes recovered.

□Concentrate□ RAD speed Stirring blade Flotation degree BPL Recovery BPL (rpm) Size (%)
(ch) 600 large
6ro, 8 79.4675
Large 65.5 87.7400
None 70. Q90.
9520 Na□shi 66.8
95.2675 Small 64.
4 90.0420 small
66.1 90.9 Example 6 BPL was separated from moderately crushed phosphate ore (-14 to +20 mesh) in the most efficient manner.

The apparatus of Example 1 and a flotation machine designed by Denver Equipment were used in comparison. Fatty acids were added to increase flotation. The results showed that a significantly higher BPL recovery was achieved with the flotation machine of the present invention. The recovered BPL flotation degree was 70-72 bar centimeter for the Schete test.

Fatty acid BPL recovery RA'D 1.0 88.5 Denver 1.0 70.6RA D
1.2 91.8 Denver 1.2 77.7RA D
1.6 95.6Denve
r 1.6 90.3 Example 4 The flotation status of various mesh sizes of Iowa coal was measured using the apparatus of Example 1. The results showed that coal of any size could be floated well.

Coal size Air flow Yield Ash Sulfur (scfh) RPM (chil)
BTU/lb (ch) (%) -66+150
24 560 91 12.306 11.3213
-150+325 24 560 - 12. ? 75
12B 33-325 24 560 93
12.627 124 2β

[Brief explanation of drawings]

1 and 2 are diagrams of one embodiment of the present invention. FIG. 6 is a side view of another embodiment of the invention, and FIGS. 4 and 5 are plan and side views of one embodiment of the baffle. 6 and 7 are plan and side views of another embodiment of the panful; FIG. 8 is a side view of the rotary diffuser and drive device of the present invention; and FIG. 9 is a plan view of the disc-shaped rotary diffuser. figure. 10 and 11 are top and side views of a preferred embodiment of a rotationally actuated diffuser. Figures 12-14 are side views of another preferred embodiment of a rotary actuated diffuser; Figures 15 and 16 are top and side views of the foam collector of the present invention; 1...tank, 6...horizontal panful, 6.1
2... Stirring section, 7.13... Foam collection section, 8.
... Vertical panfur, 10... Passage, 15... Vane plate, 16... Disk, 19... Motor,
21...Panful. Patent applicant Sterling Drug Incorporated (4 others) FIG, 3 FIG, 5 FIG, 6 FIG, 7 FIG 13. 1. Engraving of drawings (no change in content) (%/Kin 762υFI
G, +5 FIG +6 -A Procedural amendment May 1930 -! Patent Application No. 61 & No. 2, Title of Invention 3, Relationship with the Amendment Case Patent Applicant's Address Tori Shichi L Star Link゛゛゛゛゜゜゜゜
Door 2 Do 4, agent S, Himasa 0 mouth ice'+ g4t< s A) )”1 @+沙・1沙〔
Uλ↑Goku Tsuru

Claims (1)

[Claims] 1. #) A flotation chamber having a physically flat bottom, generally vertical side walls, a lower agitation section and an upper foam collection section; a rotatably actuated diffuser immersed therein for introducing into said liquid a gas stream in the form of bubbles having a controllable nascent diameter ranging from less than 0.05 mm to more than 10 mm; . means for injecting gas through the diffuser; and means for introducing into said chamber the raw material 5 blowing agent and other chemicals to be separated. A means for removing or recovering the bubbles of buoyant material and the dross of non-floating material. A substance selective flotation device from five liquids comprising: 2. A substance selective flotation device according to claim 1, comprising means for adjusting the rotational speed of said diffuser and/or the speed of the gas flow therethrough. 6. Means for introducing liquid/fluid into said chamber in place of the liquid/fluid removed from said chamber in said foam and/or scum; or Second
Substance-selective flotation device as described in Section. 4. A material selective flotation device according to claim 6, wherein said liquid/fluid is introduced as a stream below a rotatably operated diffuser. 5. Said flotation chamber is provided with two or more panfurs extending inwardly from the side wall thereof corresponding to the agitation section, so as to reduce the swirling motion of the liquid and to dissipate the energy of the upward gas-liquid flow. A substance selective flotation device according to any one of the preceding claims. 6. A material selective flotation device according to claim 5, wherein said panfur is vertical. Z. Two or more horizontal rows of baffles extending inwardly from opposite sidewalls, with adjacent rows of panffles affixed to the sidewalls at different angles to direct the direction of gas-liquid flow. 6. A material selective flotation device according to claim 5, wherein the material selective flotation device changes the energy of the upward gas-liquid flow. 8. The substance selective flotation device according to claim 5, wherein said baffle comprises upper and lower members arranged at different angles from the horizontal and connected to each other. 9. A substance selective flotation device according to any of the preceding claims, wherein said stirring section and foam collecting section are separated by a generally horizontal panfur around the periphery of said chamber. 10. The comatose selective flotation device of claim 9, wherein the lower surface of said horizontal panful bends from a horizontal position at its inner edge to a generally vertical position coinciding with the side walls of the flotation chamber. 11. Claim 9, wherein the top surface of said horizontal panfle tapers outwardly to form an angled wall between the inner edge of the horizontal panfle and the top edge of the vertical side wall for foam collection. Or the substance selective flotation device according to item 10. 12. Any of claims 1 to 11, wherein the device for removing or collecting bubbles of suspended material includes a continuous overflow adjacent the center of the upper foam collection section. The substance selective flotation device described. 13. The material selective flotation device of claim 12, wherein said overflow surrounds the axis of an actuated diffuser. 14. A substance selective flotation device according to any of the preceding claims, wherein said rotating diffuser is at the lower end of said hollow shaft, said shaft being supported above the surface of the liquid in said chamber. . 15. Material selective flotation according to any of claims 1 to 13, wherein said rotating diffuser is at the upper end of said hollow shaft, said shaft extending through the bottom of said chamber. Device. 16. Said rotatably actuated diffuser has a gas inlet and at least one lubricant operatively connected to said umbrella inlet;
A gas plenum is provided, at least one wall of which is perforated to allow gas to pass through this wall and exit to the outer surface of the disc-like member, thus allowing the When gas is introduced into the gas intake while the gas diffuser is rotating about its axis, the gas flows into the gas plenum. A nascent gas bubble then exits through said perforated wall and forms on the surface of said disc-shaped member, and when the disc member rotates in said liquid, said nascent gas bubble forms on the surface of said disc-shaped member. , which is sheared by the viscous shear force exerted by the liquid to form fine gas bubbles. A disk-shaped member, and the above-mentioned fine particles caused by the passage around the disk-shaped member and the turbulence in the jet after one revolution caused by the vortex originating from the edge of the disk member and the spiral outward from this edge. the ratio of the total diameter of the disc-like member to its maximum thickness in the gas diffusion portion occupied by the gas plenum is at least about 10:1 to minimize coalescence of shear bubbles;
A substance selective flotation device according to any one of claims 1 to 15, which refers to means including the disk-shaped member. 17. Claim 16, wherein said gas inlet is a hollow shaft and said gas plenum is located on said disc-shaped member mounted on said shaft perpendicular to its axis of rotation.
Substance-selective flotation device as described in Section. 18. A substance selective flotation device according to claim 16 or 17, wherein said disk-shaped member is placed in a recess in the floor of said chamber. 19. The substance selective flotation device according to claim 18, wherein the upper surface of the disc-shaped member is flat. 20. Claims 16 through 20, wherein the ratio of the overall diameter of said disc-shaped member to its maximum thickness in the gas diffusion portion occupied by said gas plenum is at least about 48:1. The substance selective flotation device according to any one of items 19 to 19. 21. The ratio of the overall diameter of said disc-like member to its maximum thickness in the gas diffusion portion occupied by said gas plenum is at least about 256:1. Material selective flotation device. 22. A material selective flotation device according to any one of claims 16 to 21, characterized in that both walls of said gas brinum are perforated through which the gas passes. 2) A substance selective flotation device according to any one of claims 16 to 22, wherein the upper and lower surfaces of the disc-shaped member are substantially parallel to the pressure plate over their entire area. 24. Said σ) The outer edge part of the disk is teno-
22. The material selective flotation device of claim 21, wherein the material selective flotation device has a reduced thickness. 25, ``The stirring blade is attached to the upper surface of the disk and/or
Or increase the agitation energy exerted by a 5-turn diffuser mounted on the bottom. The bubble size is also reduced by increasing the shear rate of the liquid in the perforated wall.
σ) Substance-selective flotation device described in any of Items 6 to 24. 26 Any of claims 16 to 25, wherein the area and/or porosity of the perforated wall is controlled so that the size of the bubbles ranges from 0.05 mm or less in diameter to 10 mm or more. Substance selective flotation device according to claim 1.