US1945786A - Centrifugal apparatus - Google Patents

Description

Feb. 6, 1934. A, PELTZER Er AL 1,945,786

CENTRIFUGAL APPARATUS Filed Sept. 23, 1930 3 Sheets-Sheet 2 A TTORNEYS.

' Feb. 6, 1934.

A. Paul-2ER Er AL CENTRIFUGAL APPARATUS s sheets-sheet s Filed Sept. 23, 1930 INVENTOR Patented Feb. 6k, 19.34

1,945,786 CENTRIFUGAL APPARATUS Albert Peltzer, Palo Alto, Calif.,

and Albert Peitzer, Jr., Chicago, Ill., assignors to Merce Centrifugal Separator Co. Ltd., San Francisco, Calif., a corporation of California Application September 23, 1930 Serial No. 483,874

5 Claims.

This invention relates generally to centrifuge apparatus and methods such as are utilized for separating components of different specific gravities in uid feed material.

It is an object of the present invention to devise a centrifuge apparatus and method which will make possible continuous operation without clogging of the centrifuge or of the discharge I ports.

It is a further object of the invention to devise a centrifuge apparatus and method which will be emcient in operation with a relatively high speed of rotation of the centrifuge bowl. In this connection the invention is characterized by a minimum amount of slippage between the walls of the bowl and the material being subjected to centrifugal force, thus making possible the use of a centrifuge bowl of relatively small diameter operating at relatively high speed.

Another object of the invention is to devise an apparatus and method of the above character which will make possible a relatively clean separation between heavier and lighter components of a iiuid feed. In attaining this object the invention is characterized by the maintenance of a zone of separation substantially free of turbu lence, and when the method is practiced as in the preferred form described herein, heavier solid components being separated from feed material are scrubbed with wash liquor to effectively cleanse the same of undesired solubles.

It is a further object of the invention to devise novel means for introducing a suitable material or liquid medium into the centrifuge bowl or chamber in addition to the usual uid feed.

Further objects of the invention will appear from the following description in which the preferred embodiment of the invention has been set forth in detail in conjunction with the accompanying drawings. It is to be understood that the appended claims are to be accorded a range of equivalents consistent with the state of the prior art.

Referring to the drawings:

Figure 1 is a side elevational view in cross section, illustrating machine incorporating the principles of the present invention.

Fig. 2 is a cross sectional View taken along the line 2-2 of Fig. 1.

Fig. 3 is a cross sectional view taken along the line 3-3 of Fig. 1.

Fig. 4 is a cross sectional view taken along the line 4-4 of Fig. 1.

Fig. 5 is a cross sectional view taken along the line 5-5 of Fig. 1.

Fig. 6 is an enlarged cross sectional detail take along the line 6-6 of Fig. 5. f

Fig. 7 is an enlarged cross sectional detail taken along the 'line 7 7 oi Fig. 5.

Fig. 8 is a detail in cross section and side elevation showing in an enlarged scale the ro centrifuge bowl and its associated parts.

Fig. 9 is a cross sectional detail taken along the line .fl- 9 of Fig. 8.

Fig. 10 is a detail perspective illustrating a swivel ring forming a part of the driving connection between the bowl and its driving shaft.

While the apparatus illustrated in the drawings and to be presently described in detail is in a single representative embodiment, it will be apparent that a number of distinct novel fes.- tures are incorporated which can be utilized independently or in various combinations. Likewise the method of the invention, which can best be understood after a detailed explanation of the apparatus, incorporates various features which can be utilized singly or in various combinations to improve present methods of effecting separation between components of dinerent speelde gravities. The machine as illustrated consists of a housing 10 which for ease of manufacture and assembly, has been shown formed of a number of separate parts joined together. ll'hus the lower sections 11 and 12 of the'housing are joined together by a suitable threaded connection 13, and serve to surround the rotary bowl of the apparatus. An upper housing section or neck 15 is connected to section 12 by means of threaded con nection 14, and serves in turn to connect the housing tothe stationary parts of a bearing assembly 16. This assembly is carried by a suitable support, such as a rigid arm 17. The rotary bowl of the apparatus is designated generally at 18 and is supported centrally within housing 10 by a suitable rotatable shaft 19.

The construction of the centrifuge bowl appears more clearly in the enlarged Fig. 3. For convenience in manufacture this bowl is likewise formed of two principal members or sections 2l and 22, which are secured together by suitable means such as a ring nut 24. Section 22 is formed with a. downwardly converging portion 26 and a lower downwardly divergent flange portion 27. Within the bowl sections described above there is formed the centrifuge chamber 28 within which the centrifugal action takes place. The upper walls of chamber 28 are donned by the conical shaped surfaces 29 and 31 of the bowl section 21, while the lower wall is defined mainly by the inverted conical surface of member 32 to be presently described. Y

To form suitable means for introducing feed material into the chamber 28 of the rotary bowl, an inlet pipe 33 extends into the housing seotion 15 and communicates at its inner end with a. cup 34. The position of cup 34 is fixed by a spider portion 36, which is clamped between housing sections 12 and 13. Cavity 37 in cup 34 surrounds shaft 19, and fluid material introduced into this cavity thru pipe 33 is discharged thru a depending sleeve 38. Sleeve 38 discharges into a lower second sleeve 39 of substantially larger diameter, which is mounted upon the centrifuge bowl as will be presently explained. As is evident from Fig. 1 sleeves 38 and 39 are concentric with respect to shaft 19, whereby the shaft and sleeve 39 can rotate independently of the relatively stationary sleeve 38. It will be noted that housing 10 is provided` with an annular portion 41 which surrounds sleeve 39, 'and which serves as an enclosure for the interior of the housing.

Within the centrifuge chamber there is a member 42 winch is annular in cross section, and

which preferably is provided with an inner coni? end of sleeve 39, member 42 is suitably fixed with jce respect to the centrifuge bowl in order to rotate therewith. The space 46 within member 42 and surrounding the lower portion of shaft 19, can be termed a feed chamber. In order to retain member 32 in proper position, it is shown provided with asuitable threaded connection 47 with the lower end of member 42. For discharging inaterial within the feed chamber 46 into the centrifuge chamber 28, the lower portion of member 42 is. provided with a plurality of circumferentially spaced radial ports 48 and 50. In passing from feed chamber 46 thru ports 48, the material must flow over an inner annular wier or lip 49. Material flowing thru ports 50 is delivered into chamber 28 at a plane below the level at which ports 48 discharge, for a purpose to be presently explained.

Mounted concentrically of the lower bowl section 22 there is a collar 51, which is preferably downwardly convergent and is provided with a lower iiange 52, to form an inner annular chamber 53. Formed upon the lower face of inverted conical member 32 are a plurality of radially extending ribs or vanes 54 which extend from a point in proximity with the upper edge or lip 56 of member 32, downwardly into chamber 53. As will be apparent from Fig. 9, ribs 54 in conjunction with the lower surface of member 32 and the upper adjacent surface of the lower bowl section 22, form a plurality of radially extending passages 58 for flow of fluid. The upper ends of these passages communicate with the annular space 55 about the lip 56 while the lower ends of the passages communicate with chamber 53. Therefore member 32 can be termed an impeller as it serves in conjunction with its associated parts to pump fluid material from chamber 53 into the space 55, which communicates with the main portion of chamber 28through the restricted annular orifice betweenlip 56 and surface 29.

In order to form a suitable driving connection between shaft 19 and the rotary parts of the centrifuge, a sleeve 61 is fitted upon the lower end of shaft 19 and is fixed thereto by suitable means, such as a threaded connection 63.- Sleeve 61 is in turn slidingly fitted within an outer sleeve 64, which carries the rotating parts of the centrifuge bowl. For example the lower end of sleeve 64 is shown provided with an enlarged annular portion 66, and this annular portion is shown securely clamped between the lower end of member 42 and the adjacent portion of impeller 32. The lower end of rotary sleeve 61 is formed with an annular surface 67 which is in opposed relationship with the lowen annular face 68 of sleeve 64. An annular swivel ring 69 such as shown in detail in Fig. 10, is interposed between surfaces 67 and 68. The

faces of ring 69 are provided with lugs 70 which seat in recesses provided in surfaces 67 and 68. A compressing spring 71 interposed between the lower end of shaft 19 and the lower central portion 72 of collar 32, serves to normally bias surfaces 67 and 68 together upon ring 69 with considerable force. Thus a driving connection is formed thru which-sufficient torque can be transthe feed material which is introduced by way of pipe 33. Suitable provision is also made for the separate discharge of the lighter and heavier components. Thus the upper bowl section is provided with a plurality of circumferentially spaced ports 74, which communicate with the centrifuge chamber 28 inwardly from its outer periphery. These ports serve to discharge theI overflow or the lighter separated components from the chamber. For discharging heavier separated components the lower bowl section 22 is provided with a plurality of circumferentially spaced ports or ducts 76. The upper ends of these ducts communicate with the outer periphery of chamber 28, while the lower ends communicate with the interior of bowl portion 27.

The housing 10 serves the function of catching both the lighter and heavier discharged components, and as will be presently explained, means is also incorporated in conjunction with the housing for effecting a return of heavier components back into the centrifuge chamber. Thus the overflow or lighter components discharged thru port 74 are collected into annular pocket 77 and can be withdrawn thru pipe 78. Pocket 77 is formed by an annular apron 79, which in turn is formed within the lower housing section 11 and has its inner edge extending immediately .beneath the lower surface of bowl ring 23. Depending collar 81 formed upon ring 24 in conjunction with apron 79, effectively isolates the lower portion of the centrifuge bowl from that vpart of the housing in which the lighter components are discharged, thus preventing intermixing of discharged lighter components with heavier components.

To effect delivery of fiuid material to chamber 53 and to the impeller 32, a volute structure 82 is mounted within the lower portion of housing 10.

The inner peripheral surface 83 of this volute is curved inwardly, in order to receive fluid material discharged from the lower lip 84 of the centrifuge bowl and to direct this material downwardly. A plurality of circumferentially spaced passages 85 serve to deliver material from surface 83 into a plurality of circumferentially spaced pockets 86. (Fig. 4.) Referring to Fig. 1 it will be noted that pockets 86 are formed between` the lower face of volute 82 and the adjacent annular face of the housing bottom wall 87, and that they are formed by vanes 88 carried by and depending from volute 82. Pockets 86 serve to deliver material to a cavity 89 formed between the inner portions of the volute and the housing bottom wall 87. An upstanding portion 91 of'the volute 82 forms a passageway 92, communicating with cavity 89, and serving to conduct the material into the bowl chamber 53. It will be noted that pockets 86 are inwardly divergent and that they are faced toward the direction of normalrotation of the bowl. By this construction a swirling movement is imparted to material which is discharged inwardly in to cavity 89, thus minimizing loss of kinetic energy. Likewise the flow resistance of material discharged thru passage 92 is minimized by the upward and inward curving of volute surface 93.

To permit the removal of a portion of fluid material from volute 82 the lower section of housing 10 is provided with a passageway 97, with which a discharge pipe 98 is connected. Cavity 89 is in communication with passageway 9'7 thru connected passages 99 and 101 An adjustment of the rate of outflow thru pipe 98 is made possible by the provision of a needle valve 102 by means of which flow thru passage 101 can be restrictedto a desired degree. Needle valve 102 can of course be adjusted exteriorally of the housing and is shown provided with a suitable packing gland 103. By means of another pipe connection 104 with cavity 89 (Fig. 5), it is possible to introduce varying quantities of additional material into the interior of volute 82, as for example wash water, as will be presently explained. Another pipe connection 105 communicating with cavity 89 can be connected to a suitable manometer or pressure gauge.

It is evident that different types of bearing assemblies 16 can be utilized. The particular type illustrated consists of a collar 108 xed to the end of support arm 17, and Within which a liner 109 is fitted. Sleeve 111 is formed upon and extends upwardly from housing section 15, and has a threaded connection 112 with liner 109. A suitable driving element such as a pulley 113 is engaged upon the upper end of shaft 19, and is retained in position by nut 114. threaded upon the shaft. A sleeve 116 is fitted upon the shaft below pulley 113, and has its lower end engaging a shoulder 117 formed upon the shaft. A collar 118 larger in diameter than the upper diameter of sleeve 111, and extends concentrically about the latter. A plurality of suitable bearing units 119, 121 and 122, surround sleeve 116 within the liner 109. 119 can be a roller bearing unit, 121 a ball bearing unit, and 122 a roller bearing unit similar to unit 119. An annular socket 123 serves as a support for the lower bearing unit 122, and is provided with an upper annular conical portion 124 seated upon the upper edge of liner 109. The upper bearing unit 119 is provided with a socket 126 and is disposed telescopically with respect to socket 123. A plurality of spring pressed plungers 127 are disposed within the socket 126, andpress against the lower face of the removable cover plate 128, thus serving to normally urge socket 126 downwardly. The lower bearing unit socket 123 is provided with a depending collar 129 which extends below and which is concentric with collar 118. An oil throw ring 131 is shown disposed about sleeve 116 between the lower face of pulley 113 and the upper bearing unit 119. A bearing assembly of this character will properly journal and support the weight of the rotating centrifuge parts and will permit a high speed of operation.

To explain the mode of operation of the above described machine, it will be presumed that the centrifuge bowl is being rotated at a given speed, as by means of a belt connected to pulley 113. It will also be presumed that feed material is being introduced into the centrifuge bowl thru pipes 33 at a constant rate under the control of the operator. While the apparatus can be utilized with various iiuid feeds, it will be presumed that the feed in this instance is mi1l starch", from which the solid starch particles are to be separated. The feed material enters the centrifuge chamber 28 thru radial ports 48 and 50, which impart to it considerable rotary energy, and within the centrifuge chamber separation takes place by virtue of the centrifugal force to which the rotating mass of material is subjected. Heavier separated components, which in this instance are the solid starch particles, progress to the outer periphery of chamber 28 and are discharged thru pipes '76 into the volute 82. It is of course understood that this heavier discharge material does notconsist solely of solid heavier separated components, but these solid components are mixed ,with a liquid medium to provide flow characteristics similar to a liquid, as for example water in the case of mill starch. Lighter separated components, which in this specific example will be gluten and water, will ow thru the discharge ports 74. These lighter separated components are collected by pockets 77 and discharged thru pipe 73. The heavier discharge material received by volute 82 flows downwardly thru passages 85, inwardly into cavity 89, and then upwardly thru central passage 92 into the chamber 53. From chamber 53 this discharge material is forcibly introduced into the annular space 55 of the centrifuge chamber 28, by the impeller 32.

Assuming now that the preferred features of our method are to be utilized, the heavier components returned to the centrifuge bowl by volute 82 and impeller 32, are diluted by admixing therewith a suitable liquid medium introduced at a controlled rate thru pipe 104. The nature of this liquid medium will depend upon the conditions under which the apparatus and method are to be utilized, and upon the character of the feed material. Generally speaking it should be such that its contact with the heavier separated components will not be detrimental, and its admixture 1' with the lighter components not undesirable. In the case of a feed material such as mill starch this liquid medium introduced thru pipe 104 can be distilled water. When operating upon feed material such as a spent chemical solution in which solid particles of a metallurgical pulp are suspended, the liquid medium can be spent chemical liquor. As will be presently explained, in the event that the heavier components to be separated from the feed consists of solid particles (as in the 1" example of mill starch) the liquid medium admixed with the material reintroduced into the centrifuge bowl will perform the useful function of scrubbing the heavier separated components vWithin the centrifuge chamber. Therefore this liquid medium will hereafter be termed wash liquor.

Continuing the above example in which mill starch is being treated, water is introduced thru pipe 104 at a controlled rate to form the wash Q liquor refered to above. 'Ihe heavier previously separated components of the material introduced into the centrifuge bowl by way of impeller 32 are redischarged thru pipes 76 together with heavier components directly separated from the feed material. In this connection it should be noted that the discharge passages afforded by pipes '76 are preferably substantially larger in diameter than standard practice. This is made possible by virtue ofthe fact that the passages carry not only heavier components directly separated from the feed, but also heavier components reintroduced by way of impeller 32. Thus the use of relatively large discharge passages precludes clogging of the centrifuge bowl thru packing of heavier components. While it is possible to introduce the material by way of impeller 32 at such a rate, proportioned withrespect to the rate of introduction of the feed material, so that all of this material is discharged immediately thru pipes '76 together with the components separated directly from the feed, it is preferable according to the present method to introduce this material at such a rate that a portion thereof flows inwardly from the outer periphery of chamber 28 thru the zone of separation, to be discharged together with the latter separated components thru ports 74. Thus assuming that,

the material introduced by impeller 32 consists of heavier previously discharged material mixed with a wash liquor such las water, the rate at which this material is introduced is so adjusted, and the amount of wash liquor contained therein is so controlled, that as the mixture is introduced into the centrifuge chamber it divides or splits into two portions. One portion containing the heavier previously separated components discharges thru pipes 76, and another portion consisting of wash liquor flows inwardly toward the center of rotation thru the separation zone, and

f is discharged thru ports 74 together with the lighter separated components. This method makes possible several important advantages, one of the most important of which is that it causes an energy exchange within the centrifuge chamber.

To explain what is meant by an energy exchange within the centrifuge chamber, it may be pointed out that 'in an ordinary centrifuge in which no material is introduced into the bowl in addition to the feed, the heavier components in the mass of material within the centrifuge bowl must accelerate in a rotary direction as they progress toward the periphery of the bowl. Since in the ordinary centrifuge this rotary velocity must be imparted tov the mass of material within the bowl and to the heavier components by contact with the mechanicalsurfaces presented to the material, it is apparent that as a given heavier particle progresses to the outer periphery of the bowl, it lags considerably behind the bowls actual rotary velocity. Such lagging or slippage withinthe centrifuge chamber causes eddy currents or turbulence within the separating zones, a condi.- tion which is conducive to poor separation. Such slippage may be reduced by vanes or by discs, but vanes augment turbulence while discs are not I satisfactory in treating feed materials containing a high percentage of solids. Ontheotherhand if it is assumed that a fluid material is introduced into the centrifuge bowl of the present invention by way of impeller 32, this material at its point of introduction into chamber 28 will have a peripheral velocity substantially equal to the corresponding portion of the centrifuge bowl, by virtue of vanes 54. Assuming now that a portion of this material flows inwardly of the centrifuge chamber over the upper lip 56 of the impeller, it will be apparent that the rotary velocity of each mass of such inwardly flowing material will tend to remain the same. 'I'he result will be that such inwardly flowing material will tend to lead the bowl.

From the above it will be understood that when a flow occurs in opposite directions thru the centrifuge chamber, one of a liquid medium introduced with rotary velocity thru the impeller 32, and the other of components of the feed material introduced near the center of the bowl, there will be an interchange of kinetic energy within the Iliquor introduced thru pipe 104 must also be propcentrifuge chamber and within the zone of separation.

Assuming again the above example in which mill starch is being introduced into the centrifuge chamber simultaneously with the return of separated starch together with wash water thru impeller 32, an exchange of kinetic energy will occur between the particles of starch separated from the feed and the wash liquor flowing inwardly from the periphery of the chamber, and if this exchange of energy is properly controlled the result will be that the slippage of the starch particles being separated from the feed will be reduced to substantially zero. Due to the reduction in slippage the disadvantages attendant the Vsame will also be reduced to a minimum; that is,

separation will take place in a substantially eddyless zone. Therefore with the preferred method of this invention it is possible to secure remarkably sharp separation between the heavier and lighter components. As it is also possible to operate the centrifuge bowlat relatively high rotative speeds, the immediate transfer of energy from liquid to starch makes possible a compact centrifuge apparatus of high capacity. Another material advantage results from the counter flow of wash liquor, namely that each particle being separated from the feed is received in a zone or bed of wash liquor flowing over lip 56 and is given a thorough scrubbing. Such a scrubbing action is frequently of paramount importance in securing a clean separation of heavier solid components. For example in separating starch particles from mill starch containing gluten, the starch particles are given a thorough scrubbing to remove solubles therefrom.

It is evident that the apparatus must be carefully and intelligently operated and the rates of introduction of various materials properly controlled in order to secure an energy exchange as explained above, with its resulting advantages. The adjustment of needle valve 102 determines the amount of material which is removed from the apparatus thru pipe 98. The amount of wash erly adjusted, so that a proper amount of this liquid medium flows inwardly to secure a proper energy exchange. The amount of material being introduced by way of impeller 32 is indicated to a. certain extent by the reading of a pressure gauge connected to pipe 105. In operation the pressure as indicated by this gauge may vary over wide limits responsive to different adjustments of needle valve 102, for the same rate of introf duction of feed and for the same speed of rota- 130 tion of the bowl. For certain pressures (assuming a given rate of feed and speed of rotation) the exchange of energy within the centrifuge chamber will be such that the material within the chamber will in general be lagging behind 1 the bowl, for other pressures the material within the chamber will in general lead the bowl, while for a given narrow range of intermediate pressures the material within the chamber is substantially in unison with the bowl. In the preferred l lation of separated solids, particularly within the annular space 5,5. Such scouring or racing action is facilitated because space 55 is substantially unobstructed in its entire circumferential extent.

By experimentation an operator can readily determine the proper adJustments for a given feed material and for a given set of operating conditions. Assuming a given rate of introduction of wash liquor thru pipe 104 it is possible to maintain a control over the specific gravity of the discharge material removed thru pipe 98, by adjustment of needle valve 102. Thus in general a lowered rate of withdrawal of material thru the needle valve will tend to increase the specific gravity of the heavier discharge fraction. Assuming that adjustments are once properly made for a given rate of feed and a feed of given characteristics, the apparatus will continue to operate in a state of equilibrium without further adjustments. It is of course obvious that in general the machine is operated to give a separation as clean as that desired with a capacity which is as great as can be secured under the conditions of operation.

It is to be understood that the term feed material or fluid feed material, as utilized in the present specification and the appended claims, refers to a material having liquid characteristics, as distinguished from gases. This feed material may contain heavier suspended solid particles which are to vbe removed from the feed in the form of a concentrate, solid particles which are to be separated from various solutions, solid particles of different specific gravities which are to be separated, or liquid components of different specific gravities. The apparatus and method described appear to be particularly adapted for the separation of solid particles in uid suspension and for the separation of heavier components emulsied with liquid.

In case certain feed material such as mill starch, are being treated by our apparatus, a preliminary classication can take place prior to introducingthe material into the centrifuge chamber. Thus referring to Fig. 1 it will be noted that a swirling motion is imparted to the feed material because of the tangential relationship of inow pipe 33 with respect to chamber 37. Therefore feed material owing into chamber 46 is swirlingin the direction of rotation of the centrifuge bowl, and further swirling movement is imparted by contact with the conical surface 43. The lighter classified materialv in feed chamber 46 flows over wier 49 and is discharged into the centrifuge chamber 28 while heavier material is discharged into the centrifuge chamber thru ports 50. Such a preliminary centrifugal treatment is advantageous when utilized with feed materials containing components which are detrimentally affected by suddenly applied centrifugal forces, as for example the gluten in mill starch. In the form of the apparatus illustrated, centrifugal force is gradually applied to the feed material. It will also be noted that the paths taken by the materials flowing thru ports 48 and 50 do not intersect or cross within the centrifuge chamber. This is an advantage in handling feed material containingcomponents which readily go over into colloidal form, as for example gluten. If an excess of feed is supplied to chamber 46 an overflow occurs thru opening 133, and can be recovered from pipe 134.

We claim:

1. In a continuously operating centrifuge machine, a rotary bowl having provision for the discharge of lighter separated material and -also having ports for the discharge of heavier sepseparately discharging heavier and lighter separated components, and means forcontinuously returning heavier separated components back into the rotor, said last means'including an impeller mounted upon the rotor and formed to provide an inlet chamber concentric with the rotor axis, a volute adapted to Areceive heavier components discharged from the rotor, and means for continuously conducting heavier components from the volute and into said chamber with rotary velocity in the direction of rotation of the rotor.

' 3. In a continuously operating centrifuge machine, a rotary bowl having provision for the discharge of lighter separated material and also having ports for the discharge of heavier separated material, and means for automatically maintaining stable separating conditions Within the bowl, Said last means comprising a closed circuit-flow pathfor continuously returning a portion of the heavier separated material discharged from the bowl back into the outer peripheral portion of the bowl, said path being so formed andproportioned that a change in the rate of discharge of heavier material from the rotor is immediately accompanied by a. compensating change in the rate of return into the bowl.

4. In a. continuously operating centrifuge machine, a rotor, a wall disposed within the rotor serving to divide the interior thereof into an inner separating space and an outer annularspace, said spaces being connected by a restricted annular orifice, said outer space being substantially unobstructed for its entire circumferential extent, means for introducing a iiuid feed into said inner space, vmeans for discharging lighter separated material from said inner space, means for eecting discharge of heavier separated material from' said outer annular space, and impeller meansfor introducing fluid material into the outer space with substantiallyv rotary velocity.

5. In a continuously operating centrifuge machine, a rotor, a wall disposed within the rotor serving to divide the interior thereof into an inner space andan outer annular space, said spaces being connected by a restricted annular orice, said outer space being substantially unobstructed for its entire circumferential extent, means for introducing-a uid feed into the inner space,-

\means for discharging lighter separated material from the inner space', means for effecting discharge of heavier separated material from'the

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