GB2096477A - Energy efficient phase transfer/dispersion systems - Google Patents

Abstract

A method or apparatus for generating gas bubbles of relatively small and uniform size in a liquid medium utilises at least one rotatable member free of fins, blades or other mixing projections, e.g., in the shape of a disc or ring 16, which is rotated in a liquid medium at an edge velocity of at least 80 feet per second. A source of gas or some other fluid phase is provided proximate to the rotatable circular members to form the bubbles.

Description

SPECIFICATION Energy efficient phase transfer/dispersion systems and methods for using the same The present invention relates to methods and apparatus for the production of dispersed fluid phase in a liquid medium for the purpose of promoting phase transfer into the liquid. The present invention performs this with high energy efficiency and with greatly improved phase transfer efficiency. The present invention also relates to the production and use of small gas bubbles for purposes other than gas transfer, as for example, the separation of solids from a liquid medium by flotation.

Aeration is the largest energy consuming component of our nation's present means for water pollution control. Aerators are extensively used to maintain aerobic conditions for sewage digestion and a host of other biological waste treatment processes.

Often, aeration equipment operates to provide mixing within biological reactors and to prevent the settling of solids. A conventional aerator is usually of high capacity (10-100 horsepower) and includes a large, finned, rotating turbine whose diameter might range from 20-60 inches (50-150 centimeters). Such units usually have efficiencies of about 1.5-1.7 pounds of oxygen transferred for each horsepower hour of energy expended. A typical 25 horsepower aerator might transfer about 1000 Ibs. of oxygen each day into the surrounding fluid. A more elaborate approach involves forcing the gas, sometimes pure oxygen, through a porous disc immersed in the fluid, creating an exhaust of fine bubbles.

Several advanced aerators have been developed which include specially shaped and finned turbines of smaller size than the conventional rotors mentioned above. Another type incorporates a large rotor operating close to a stator with air sheared in the space defined between the two opposing pieces of metal. Such aerators have achieved up to about 2.65 Ibs. oxygen transferred per horsepower hour, or roughly 65% better energy efficiency than conventional aerators.

The capital cost of aeration equipment is related to the size of the motor used because the motor is the major cost component in most systems. The other major costs are for the installation of the unit and for the supply of electrical power. Any major change in the efficiency of an aerator produces not only operating cost savings by reducing energy consumption during treatment but also substantially decreases capital costs for the equipment by reducing the size of the motor required for a given amount of aeration capacity. An aerator with a two-fold increase in efficiency and a design similar to that of a conventional aerator, would reduce operating costs by almost 40% and capital costs for the system by a factor of 30%.

The major aim in most systems of conventional design is to maximise turbulence (surface aerators) and increase the inter-facial surface area between the liquid and gas (assumed to be air or oxygen in most cases). Advanced aerators usually are designed to produce small bubbles as they have large surface areas and slow rise velocities. Such small bubbles remain in contact with the fluid for a long period of time and greatly improve gas to liquid transfer. Generating small bubbles, rather than promoting surface turbulence, is a better approach to more efficient aeration. Small bubbles can also be used for flotation (solid/liquid separtion), protein extraction by the concentrating of surface-active solutes in the bubble membrane, or for densitydependent separation. Accordingly, an efficient small-bubble generator could be applied to many uses.However, the energy costs of most smallbubble generators prove prohibitive. It is an object of the present invention to provide an energy efficient small-bubble generator.

The present invention provides an energy efficient apparatus for generating small bubbles with high interfacial surface areas in a liquid medium to enhance the transfer of components from the fluid phase into the liquid. The apparatus includes a rotatable member, such as a disc or ring, and means for rotating the member within the liquid to provide an edge velocity of 80 feet per second or greater. Means are provided proximate to the rotatable member for supplying the fluid phase to be dispersed into small bubbles in the liquid. Preferably, when a disc is used, its diameter should be less than 12 inches. Optimum relationships between disc or ring size and speed of rotation can be utilized in the apparatus to optimize the rate of phase transfer to the liquid relative to the energy required to operate the apparatus.The apparatus is useful for performing various gas to liquid transfer processes, such as aeration of wastewaterfor promoting decomposition of biological waste products, production of stable foam products, and carbonation of soft drinks. Also, processes for separation of solids from liquids by flotation resulting from the buoyancy of the small bubbles can be achieved with the apparatus.

Figure 1 is an elevational view in section of a first embodiment of an apparatus for producing gas bubbles in accordance with the present invention, Figure 2 is a perspective view of a second embodiment of an apparatus for producing gas bubbles in accordance with the present invention, Figure 3 is an elevational view of one embodiment of an aerating ring used with the apparatus of Figures 1 and 2, Figure 4 is a bottom plan view of the aerating ring of Figure 3, Figure 5 is an elevational view of an embodiment of an aerating disc used with the apparatus of Figures 1 and 2, Figure 6 is a top plan view of the disc of Figure 5, isolated from its drive shaft and cowling, Figure 7 is a top plan view of a moving aerator rim having a stationary supporting center used with the apparatus of Figures 1 and 2, Figure 8 is an elevational view of a flexible belt driven by a motor vertically through a duct and horizontally along a ring drive in accordance with the present invention, Figure 8A illustrates a ring drive for the flexible belt as seen looking down line 8A-8A of Figure 8, and Figure 9 is a graph illustrating the relative efficien cies of similar sized discs and rings showing the greater efficiency of a ring.

A gas bubble contains a certain amount of energy associated with the surface tension of its walls. If a bubble fissions into two bubbles, the total volume remains unchanged, but the total surface area increases. Thus, the process of fissioning requires energy, and the dominant source of energy is kinetic energy in the shear flow of the surrounding fluid.

Fluid pressure does work on parts of the bubble, while other parts of the bubble do work on the fluid.

The quantity of work done by the fluid on the bubble during the fissioning process is proportional to the bubble volume multiplied by the pressure, and can be expressed by the relationship Work in a rb5S2d where rb is the bubble radius, S is the shear flow, and d is the fluid density.

The work done by the bubble on the fluid can be expressed as Work out = rb2 C#4 rr (21/2 1) where rb is the bubble radius and Cr is the surface tension of the bubble.

Because the fission process is reversible, the work in must equal the work out. Thus, for a given shear flow, bubbles will shear until they come to an equilibrium radius determined by: rb3S2d/ < r= constant, in which the constant is the Weber number, W, of the system. Accordingly, it has been determined that the smallest bubbles are produced by the flows of high est shear.For a rotating object of radius R spinning atQ RPM, the bubbles produced have a radius of: rb= 6.613 (RQ)-2~3 where rb and R are given in centimeters, and the rotating object is generally wetted by the surround ing fluid either because of the presence of wetting agents in the fluid (surfactants) or because of the natural wettabilityofthe roating object by the surrounding fluid. The bubble size remains large until the surface is made to wet effectively. Without wetting, the device is generally incapable of producing the very small bubbles which allow it to perform so efficiently.

It has further been empirically determined that the dissolved gas transfer efficiency for gas transfer to a fluid is in many cases approximately inversely linearly related to the gas bubble radius for gas bubbles less than about 75 micrometers in diameter.

That is, the transfer efficiency (TE) linearly decreases as the size of the bubble increases according to the relationship: TE= 1- krb where k is a constant Thus, the efficiency of small bubble generators is related to the bubble size. The smaller the bubbles produced (and thus the greater the interfacial sur face area between the liquid and the gas), the more efficient is the gas transfer from the bubble to the liquid.

The amount of gas that can pass through the shear field created by the rotating disc or ring at steady state is: Qmax(ml/min)= 8 7r3R2Q rb where R and rb are in centimeters. The total amount of gas transferred is: Qmax-TE However, it has been further determined and experimentally confirmed that the power required to rotate a disc in a viscous medium rapidly increases with increasing disc size and speed of rotation according to the equation: HP 2 59 x 10x13R4fl5# where HP is shaft horespower required to drive the disc. The result is that small, efficient spinning disc aerators will not scale up to large efficient aerators because energy consumption increases rapidly with increasing disc size but aeration capacity does not.

As noted above, shear flow is the factor that determines bubble size. The shear flow at the edges of larger and smaller rotating discs will be the same provided the edge velocities are equivalent. However, the larger disc has a larger rotating surface which increases the viscous drag upon that disc, reducing its efficiency (see Figure 9).

In addition, while turbine blades, fins, and other propeller-like additions to the rotating body increase mixing, they act to further increase the amount of energy required to rotate the disc. As such, such modifications tend to reduce the overall efficiency of gas transfer and are undesirable.

As will be discussed below, one solution to the above problem is to provide a bubble generator including a plurality of small rotatable discs. A second solution to the problem is to provide a bubble generator utilizing rotatable rings, not discs. Rings, which do not have large rotating centers, do not exhibit as rapid an increase in viscous drag as rotat ing discs of corresponding dimensions. In fact, the energy required to rotate a ring is given as: HP (ring) R3n 2 (6.67 x 1011) Accordingly, a smaller, efficient ring aerator may be scaled into a larger ring that remains highly efficient (see Figure 9).

The optimization of disc parameters to achieve optimum efficiency of disc aerator has been both analytically and empirically determined to be as follows: Q= 31239/R, where R = disc radius in centimeters and Q = RPM.

The above relation results in an optimization of the device energy efficiency as a function of disc radius given as follows: F= P/VR, where F is the ratio of the Dissolved Oxygen Transfer Rate (DOTR) divided by the amount of power consumed to rotate the disc and P is a constant. Simply stated, the efficiency of a disc aerator decreases as the radius of the disc increases.

The gas bubbles produced by the optimized disc parameters are in the order of substantially rub = .0067 cm., where rb = bubble radius.

Likewise, optimized ring parameters have been determined as follows: RPM = 41067/R, F= constant and Tb= .00556cm.

When the above optimization equations are differentiated to determine the conditions for optimum fluid phase transfer, it is determined that an edge velocity of at least approximately 80 feet/second or greater required.

Note that in the case of the ring, the energy efficiency, F, remains constant regardless of ring size while this is not true in the case of disc-based devices.

However, the radius of the ring may be increased, and its speed of rotation correspondingly decreased to conform to the derived optimization criteria without affecting its efficiency because the energy efficiency, F, of ring-shaped devices remains constant regardless of size. To the contrary, increasing the radius of a disc while correspondingly decreasing its speed of rotation to conform to the derived optimization criteria will result in a decline in the efficiency of the system because the energy efficiency, F, of discshaped devices is inversely proportional to the square root of their radius. As discussed above, increasing the size of a disc rapidly increases its drag to reduce its overall efficiency. This is not the same with a ring which has an open center and does not create increasing drag with increasing size.The relative efficiencies of similar sized discs and rings are compared in Figure 9, which will be discussed below.

It has also been determined that the size of the disc or ring is preferably related to its rotational speed.

For example, R = K/RPM for a disc and, R = M/RPM for a ring, where R = disc or ring radius in centimeters, RPM = speed in revolutions per minute K = a constant between 20,000 and 45,000 and, M = a constant between 25,000 and 55,000 Also, preferably the fluid phase transfer rate into the liquid medium is: GasFeed < N# R2rb, N is a constant of approximately 0.20 Gas Feed is in liters/minute, Q= RPM, R = disc or ring radius, and rb is bubble radius.

The embodiments of the present invention, to be discussed below, includes specific apparatus for generating small bubbles (of the order of 100 micrometers or less in diameter). The apparatus are designed to use the theoretical considerations discussed herein to provide an energy efficient, highspeed apparatus emphasizing the generation of small bubbles and high inter-facial surface area while minimizing turbulence and mixing, to enhance the efficiency of phase transfer and dispersion.

Figure 1 illustrates a first possible embodiment of an apparatus for generating small gas bubbles in accordance with the present invention. A support collar 2 is mounted to the top of a watertight housing 4. A motor 6 is mounted within the housing on a motor support 8. The motor support is itself supported by a base plate 10 mounted to the inner surface of the bottom of the watertight housing.

A drive shaft 12 extends downwardly from motor 6 through suitable openings provided in the base plate 10 and the lower end of the housing, A gasket 14 seals the opening in the base plate to prevent any liquid from entering the housing.

A rotatable circular member 16 is affixed to the end of the drive shaft extending outward from the housing. Although the rotatable member is shown as being a disc in Figure 1, a ring may also be employed, as will be discussed below. A compressor (not shown) is provided to supply a gas both above and belowthe disc 16. The rotatable member is generally flat or smooth to inhibit mixing or turbulence of the fluid medium. It does not include blades or fins which promote agitation. The rotatable member is adapted to be wetted by the fluid medium.

In operation, the lower portion of the watertight housing is immersed in a liquid, wetting the rotatable member, and the motor and compressor are actuated. For the reasons discussed above, the motor is rotated at a rate sufficient to provide the disc 16 with an edge velocity of at least 80 feet/second. The disc diameter should be no greater than 12 inches and, preferably, about 4 inches. The shear flow created by the rotating disc results in the dispersion of the gas as small bubbles, resulting in a highly efficient transfer of the gas supplied by the compressor into the liquid medium in which the rotating disc is immersed.

Figure 2 of the drawings illustrates a second embodiment in accordance with the present invention including a plurality of rotatable members mounted to a common drive shaft. Specifically, a motor 18 is mounted to the top end of an open-sided supporting frame 20. A cover 22 is removably mounted above the top of the supporting frame to protect the motor. A flotation device 24 is mounted to the supporting frame below the motor to support the structure in a liquid medium.

One end of a drive shaft 26 is coupled to the motor 18 through a suitable opening in the top of the supporting frame 20. The other end of the drive shaft extends longitudinally through the supporting frame with the lower end of the drive shaft affixed to the lower end of the supporting frame. A plurality of rotatable members 28 are mounted to the drive shaft 26 in stacked relationship. Although the members 28 are illustrated as discs, they may also be rings as will be discussed below.

A compressor or blower 30, mounted to the top end of the supporting frame 20, is driven by the motor 18 via an endless belt 32 connecting the motor drive shaft 26 with a compressor drive shaft 34 extending from the bottom of the compressor. The inlet end of a gas supply manifold 36 is mounted in fluid communication with the compressor, and a plurality of manifold tubes 38 extend from the gas supply mainfold. A sufficient number of mainfold tubes 38 are provided so that the outlet end of those tubes supply gas from the compressor both above and below each of the rotatable discs 28.

Although the compressor and manifolds of the above apparatus may be omitted by providing a self-aspirating system using a hollow drive shaft 26, this modification is not normally recommended. The relatively large diameter hollow motor drive shaft which would be required for a self-aspirating system is not compatible with the relatively small diameter discs necessary to the efficiency of the rotating disc apparatus.

Also, although the means for rotating the shaft is shown as a motor, it is within the scope of the pres entinventionforthe rotatable member to be the rotor of an induction motor surrounded by stator coils or other electromagnetic induction means.

In operation, the support frame 20 is immersed in a liquid medium up to the level of the flotation device 24. The motor 18 rotates at a speed sufficient to obtain disc edge velocities required to obtain near optimum performance, namely, 80 feet/second or greater. The resulting apparatus provides a highly efficient transfer of gas supplied by the compressor to the liquid medium, in accordance with the optimization equations discussed above.

In Figures 1 and 2 embodiments of the invention, the rotatable members are discs. However, as noted in the discussion of those two drawings, the rotatable discs may be replaced by rotatable rings. In fact, it is desirable to use a ring configuration as opposed to a disc. The graph of Figure 9 compares the efficiencies of similar sized rings and discs. It is apparent that although the efficiency of the ring is independent of its size, the efficiency of the disc decreases as disc size increases.

The size of a ring may be larger than that of a disc because, as discussed above, the open center of a ring does not create the efficiency reducing viscous drag exhibited by a disc. In any event, the speed of rotation and the size of the ring are governed by the ring optimization equations discussed above.

Figures 38 illustrate in detail examples of various discs and rings which may be used in the apparatus of Figures 1 and 2. Figures 3 and 4, show a ring that may be used as the rotatable member in the embodiment of the invention shown in Figures 1 and 2. A rigid ring or flexible loop 40 is driven by a motor 42 via a drive shaft 44. The drive shaft is coupled to a drive pulley 46 located adjacent the inner surface of the ring. Two idle pulleys 48 and 50 are located at different positions adjacent to the inner surface of the ring. The means for providing gas (e.g., the compressor or manifold tubes) supplies gas proximate the open center of the ring. Because the center of the ring has no structural components, no viscous drag is realized at the center. Multiple rings can be stacked and driven from a single power source and drive shaft in such a configuration.

Figures 5 and 6 illustrate a side elevational view and a top plan view of a disc that may be used as the rotatable member in the embodiments of the invention disclosed in Figures 1 and 2. The disc 52 is coupled to a motor (not shown) by a drive shaft 54. A cowling 56 is provided both above and below the disc 52 to keep fluid away from the disc except at its rim. The disk may be affixed to the drive shaft by spokes (not shown). The fluid media to be dispersed in the surrounding liquid is supplied through the cowling to the rim of the disc. Because the viscosity of gas (i.e., air) is approximately 1/100 the viscosity of liquid (i.e., water), the air cowling 56 tends to eliminate viscous drag on the center of the disc and approximates the behaviour and performance of a ring-based apparatus.

Figure 7 illustrates what may be referred to as a "chainsaw" aerator shown generally by the reference numeral 58. The apparatus includes a stationary centerpiece 60 and a rotatable rim 62 driven by a motor 64. The rotation of the rim in a liquid results in the formation of a high shear flow proximate to this rim and a fluid phase released proximate to this moving rim will become dispersed in accordance with the present invention. Because the centrepiece 60 does not move, it does not produce viscous drag, thereby reducing the overall power consumption of the system.

Of the devices discussed with respect to Figures 3-7, the design concept as outlined in Figures 3 and 4 is preferred because it will introduce the least drag and thus decrease the power consumption necessaryto operate the phase dispersion system. The cowling shown in Figure 5 and the stationary center of the device shown in Figure 7 will introduce drag because they are stationary and the liquid surrounding those respective elements is in motion.

Figures 8 and 8A illustrate a further embodiment of an apparatus in accordance with the present invention. A motor 66 and a compressor (not shown) mounted behind the motor are both mounted atop a flotation support 70 formed for example, from foam plastic. The compressor is coupled to the motor via a drive sheave 68, so that actuation of the motor also drives the compressor. The motor also drives an endless belt or loop 72, formed from flexible material such as a cord, band, cable, or rope, through a substantially vertical duct 74 having two vertical pulleys 73 mounted at the bottom of the duct. At the bottom of the duct after passing one vertical pulley 73, the belt bends 90 and continues around a horizontal ring 76, formed from six hexagonally situated pulleys 78 mounted on arms 80 extending from a central hub 83.Each arm is equipped with a shock absorber 86. The central hub 83 is mounted to the duct by an arm 81. The belt, after completing a rotation around the hexagon, again bends 90 and travels back up the duct to the main drive sheave 88 attached to the motor. Gas is transmitted from the compressor, through the duct, and out a gas outlet 90 located approximately in the center of the hexagon. Rotation of the belt 72 in a liquid medium and introduction of gas at the center of the belt creates the effect of a high speed ring resulting in phase transfer of the gas into the liquid.

The embodiments of the invention illustrated in Figures 1 -8A provide apparatus for generating small bubbles which increase the efficiency of phase transfer and dispersion and reduce the power consumption of the transfer process. The embodiments of the apparatus are useful in the following processes in which a gas to fluid transfer is required.

1.) AERATION: Dispersion of oxygen or air in wastewater for the purpose of promoting the aerobic decomposition of biological waste products.

2.) VOLATILIZATION: Related to aeration but designed to remove a volatile component from a fluid. For example, the removal of halocarbon impurities in drinking water.

3.) GAS SCRUBBING: The separation of one gaseous component from another by dispersion in an absorbing fluid and selective stripping or gases. A typical example is the removal of carbon dioxide from synthesis gas produced from coal gasification or the removal of sulfur dioxide from fossil-fuel burning power plant stack gas.

4.) GAS DISPERSION IN REACTIVE FLUIDS: Gas dispersion into a fluid containing a catalyst or reactant that promotes chemical reactions or changes.

For example, the dispersion of synthesis gas from coal gasification into a fluid slurry containing a catalyst that promotes the formation of methane or methanol from those gases. Other examples are dispersion of ethylene and oxygen in a catalytic slurry to produce ethylene oxide gas, dispersion of a monomer into a fluid for the purpose of promoting polymerization, or dispersion of a gas such as hydrogen sulfide to preceipitate heavy metals or a gas such as carbon dioxide into a solution of sodium hydroxide to produce sodium carbonate. Another use might involve a small unit to disperse automobile exhaust gases in a catalytic slurry or homogeneous-phase catalyst to reduce exhaust emissions of nitrogen oxides and carbon monoxide.

5.) FLOTATION: Production of small bubbles for use in flotation processes where solids are separated from a liquid. Examples might include the separation of sewage sludge from water, the collection of algae from seawater, the removal of lighter coal particles from heavier mineral-containing particles (coal cleaning). As the size of bubbles decline, their attraction for solutes from the surrounding solution and their attraction to solid surfaces increases. This increasing force of attraction soon becomes sufficienctly strong that small bubbles are capable of sticking to solid surfaces with sufficient tenacity to overcome the disruptive influence of random fluid shear fields. At this point, the bubbles become attached in a stable manner to small or even large solid bodies floating in the fluid and apply their net buoyancy to 'float' the solids to the surface of the fluid body.

6.) SURFACE-ACTIVE AGENT RECOVERY: Small bubbles can be used to recover surface-active com ponentsfrom a solution by taking advantage of the tendency for surface-active materials to be concentrated within the membrane of the bubbles. Small bubbles, by virtue of their high surface area and higher rate of curvature, have a greater capacity to remove such materials from solution. Examples include the use of devices like those described herein to produce bubbles that form a foam containing proteins (removed from wastewaters such as potato juice, whey, and milk wastes), or for the recovery of detergents, or collection of low-level quantities of organic materials from seawater. This is possible because of the formation of an excess surface concentration, C, of surface-active components within the gas-liquid interface.The excess surface concentration, given in mol/m2 of surface, can be thermo-dynamically related to the bulk properties of the fluid as shown by Gibbs.

Where Cr is the surface tension, c is the concentration of the active component in the bulk fluid, R is the universal gas constant and Tthe absolute temperature. For large molecules it is especially important to account for the difference between concentration and actual solute activity such that it is more correct to replace c with a measured activity for the proteins or other macro-molecules being extracted.

Generally, it can be seen that the surface energy of a very small bubble is considerably higher than for large bubbles. Increasing the surface area of a liquid requires the investment of energy, which remains stored in the enlarged surface, just as energy can be stored in a stretched rubber band, and it can perform work if the enlarged surface is allowed to contract again. Decreasing the surface tension by introducing surface-active solutes to the bulk fluid allows this work to be expended in the form of concentrating these solutes against a concentration gradient. Thus, an excess surface concentration is developed at the gas/liquid membrane and the amount of material collected depends upon the production of copious bubble surface membrane area.Similar reasoning also helps explain why bubbles are attracted to surfaces that can also serve to reduce the interfacial energy of the bubble atthe point of contact.

7.) PRODUCTION OF STABLE FOAM PRO DUCTS: The high shear field systems can be used to produce stable foam products such as foamedurethane and light-weight closed-cell plastic foams.

8.) SOFT-DRINK CARBONATION: The systems described herein can be used to decrease the time required to produce carbonated soft drinks by speeding up the dispersion of carbon dioxide.

9.) SEPARATION OF OCEAN BIOMASS: Efficient small bubble production systems can be used to harvest biomass from the ocean. Ozone is mixed with air and supplied to the rotatable member of a bubble generating apparatus, as discussed herein. A plurality of gas bubbles (of the order of size of 50-80 micrometers in diameter) are formed and contacted with water containing the biomass to be harvested.

The ozone gas acts to convert the surfaces of the biomass to be harvested into more hydrophobic form. The plurality of bubbles cause the biomass to rise due to the principles discussed above relating to separation of solids from liquids.

Claims (28)

1. An apparatus for generating high interfacial surface area in a liquid medium and for enhancing phase transfer thereto of the type comprising at least one member rotatable in said liquid medium, means for rotating said rotatable member and means for supplying a fluid phase medium proximate to said rotatable member, characterized in said rotatable member has generally smooth upper and lower surfaces for inhibiting mixing of said liquid medium as the member is rotated and is adapted to be substantially wetted by said liquid medium, and said rotating means rotates said rotatable member in said liquid medium such that the edge velocity of said rotatable member is 80 feet/second or greater, and whereby rotation of said member in said liquid medium produces a high shear field that increases the interfacial area between the fluid phase and the liquid medium with minimal energy expended on creating turbulence and mixing.

2. An apparatus as claimed in Claim 1 characterized in that said rotatable member is a generally flat and smooth disc, the diameter of said disc being no greater than twelve inches.

3. An apparatus as claimed in Claim 1 characterized in that said rotatable member generally is in the shape of a ring.

4. An apparatus as claimed in Claims 2 or 3 characterized by a drive shaft coupled to said means for rotating, and a housing for enclosing said means for rotating and the upper portion of said drive shaft, the lower portion of said drive shaft extending outwardly of said housing through an opening defined in said housing, said rotatable member being coupled to the end of said drive shaft extending outwardly of said housing.

5. An apparatus as claimed in Claims 2 or3 characterized in that said means for supplying said fluid phase medium is positioned to supply said fluid phase medium proximate to the upper and lower surfaces of said rotatable member.

6. An apparatus as claimed in Claim 5 characterized in that said means for supplying said fluid phase medium is a compressor.

7. An apparatus as claimed in Claim 5 characterized in that said means for supplying said fluid phase medium is a blower.

8. An apparatus as claimed in Claim 5 characterized by means for coupling said means for supplying to said means for rotating such that actuation of said means for rotating simultaneously actuates said means for supplying.

9. An apparatus as claimed in Claim 5 character ized by a gas supply manifold having its inlet end coupled to said means for supplying, and at least one outlet tube, coupled at its inlet end to said gas supply manifold, the outlet of said tube being positioned proximate to said at least one rotatable member.

10. An apparatus as claimed in Claims 2 or3 characterized by a plurality of said rotatable member, are mounted in stacked relationship to a single drive shaft coupled to said means for rotating.

11. An apparatus as claimed in claims 2 or3 characterized in that said means for supplying said fluid phase are limited so as to supply a volume of said fluid phase at a rate substantially limited to: GAS Feed (liters/minute) < NQ R2rb where N is generally equal to 0.20 Q= RPM R = disc or ring radius, and rb is bubble radius

12. An apparatus as claimed in Claim 9 character ized by a plurality of manifold tubes, the inlets of said manifold tubes coupled to said means for supplying gas in fluid communication relationship therewith, the number of said plurality of manifold tubes being sufficient such that there is at least one of said manifold tubes proximate to each of said rotatable members.

13. An apparatus as claimed in Claim 12 charac terized in that said means for supplying is a compressor, and means for coupling said compressorto said means for rotating such that actuation of said means for rotating simultaneously actuates said compressor.

14. An apparatus as claimed in Claim 12 characterized in that said means for supplying is a blower, and means for coupling said blowerto said means for rotating such that actuation of said means for rotating simultaneously actuates said blower.

15. An apparatus as claimed in Claim 2 characterized by a cowling mounted proximate to said disc so asto separate said disc from said liquid medium at all positions on said disc other than at its periphery.

16. An apparatus as claimed in Claim 15 characterized in that said means for supplying is coupled to said cowling in fluid communication therewith such that said fluid phase is supplied proximate said rim of said disc through said cowling.

17. An apparatus as claimed in Claim 1 characterized in that said rotatable member comprises a stationary center portion and a rim rotatable around said stationary center.

18. An apparatus as claimed in Claim 1 characterized in that said rotatable member is an endless loop of flexible material rotated along the peripmeter of a substantially open centered supporting structure to create the effect of a high speed rotating ring.

19. An apparatus as claimed in Claim 1 characterized in that said rotatable member is a disc, and the radius of said disc is substantially related to the speed it rotates as: K R= RPM where K > 20,000 and generally less than 45,00 and where R= disc radius in centimeters, and RPM = the speed of rotation of said disc in revolutions per minute.

20. An apparatus as claimed in Claim 3 characterized in that the radius of said ring is substantially related to the speed it rotates as: M R= RPM where M > 25,000 and generally less than 55,000 and where R = the ring radius in centimeters and RPM = the speed of rotation of said ring in revolutions per minute.

21. A method of dispersing a fluid phase in a liquid medium and generating high interfacial surface area in said liquid medium by rotating a member in the liquid medium and supplying a first fluid phase to be transferred or dispersed proximate said rotating member, characterized in that said member is generally smooth, lacking blades fins or other shapes to enhance mixing, is substantially wetted by the surrounding liquid medium and is rotated within said liquid medium at a speed suffi cient to provide high edge velocity of 80 feet per second or greater, whereby said rotating member produces a high shear field resulting in a fine dispersion of the fluid phase in said liquid medium.

22. The method of Claim 21 characterized in that said rotating member is a disc of 12 inches or less in diameter.

23. The method of Claim 21 characterized in that said rotating member is a ring.

24. The method of Claim 21 characterized in that said second phase fluid is supplied proximate to both said upper and lower surfaces of said rotating member.

25. The method of Claim 21 characterized by the step of: rotating a plurality of generally smooth members mounted to a common drive shaft in stacked relationship in said liquid medium.

26. A method of separating solids from liquid comprising the steps of rotating a member and supplying a gas proximate to said rotating member to generate small gas bubbles in said liquid, characterized in that said member is smooth, lacking blades, fins and other shapes used to enhance mixing, is substantially wetted by the surrounding liquid medium, and is rotated in said liquid at a speed sufefficient to provide high edge velocities of 80 feet per second or greater; said gas bubbles being of a sufficiently small size to become attached in a stable mannerto said solids, the buoyancy of said gas bubbles causing said solids to float to the surface of said liquid.

27. A method of harvesting biomass from the ocean comprising the steps of rotating a member and supplying a gas to said rotating member; characterized in that said member is lacking blades, fins, and other shapes used to enhance mixing, is substantially wetted by the surrounding liquid medium, is rotated proximate to said biomass at a speed sufficient to provide high edge velocities of 80 feet per second or greater, and said gas is preferably a mixture of air and ozone such that such gas produces a plurality of gas bubbles near said biomass to convert the surfaces of said biomass into more hydrophobic form, and said plurality of gas bubbles becomes attached to said biomass to cause it to float to the surface where it can be collected.

28. A method of dispersing a fluid phase in a field slurry by generating high inter-facial surface area and promoting phase transfer, the steps of said method including rotating a member and supplying a fluid phase to be transferred or dispersed proximate to said rotating member, characterized in that said member is generally smooth and lacking blades, fins and other shapes used to enhance mixing, is wetted by the surrounding liquid medium and is rotated within said fluid slurry at a speed sufficient to provide high edge velocities of 80 feet per second or greater, and said rotating member produces a high shear field resulting in a find dispersion of the fluid phase in said fluid slurry medium.