US2917228A - Pressured centrifuge - Google Patents

Description

Dec. 15, 1959 K. D. LEWIS ETAL PRESSURED CENTRIFUGE Filed Nov. 27, 1956 4 Sheets-Sheet 2 & k h m Y Q 0M 6 M 2 2 T .DH f R 6 6 WhS O vrflwm n W m MM A mmc Y B Dec. 15, 1959 D. LEWIS ETAL PRESSURED CENTRIFUGE 4 Sheets-Sheet 3 Filed NOV. 27, 1956 INVENTORS Oscar W. Johnson Kenneth D. Lewis Charles H. Scofl BY QWJM a 1! Wanmrnwm ATTORNEY PRESSURED CENTRIFUGE Filed Nov. 27, 1956 4' Sheets-Sheet 4 llllll Fig. 9;

59 l 72 69 L jg I I INVENTORS I08 I07 Oscar W. Johnson Kenneth D. Lewis Charles H. Scofl Fig. IO. m; pa

ATTORNEY United States Patent F PRESSURED CENTRIFUGE Kenneth D. Lewis, San Mateo, Calif., Oscar W. Johnson, Houston, Tex., and Charles H. Scott, South Norwalk, C'onm, assignors to Don-Oliver Incorporated, Siam ford, Conn., a corporation of Delaware Application November 27, 195.6, si rial No. 624,524 4 Claims. (Cl. 233-1) This invention relates generally to centrifuges of the type adapted for the continuous separation and discharge of separated underflow and overflow fractions from a feed material containing suspended material. More particnlarly, the invention relates to improved ways and means enabling operation of such machines at elevated pressures.

In general, the invention relates to centrifuges of the type disclosed in Patents Nos. 1,923,454, "1,847,751 and 2,060,236, which comprise generally a rotor housing, a rotor suspended in such housing and mounted for rotation therein on a central shaft, said shaft being journalled for rotation in bearings at one or both endsland such bearings being mounted functionally remote from the rotor "housing in order to protect them from deleterious effects of material being separated in such housing. 7

In the usual commercial machine of .this character there is provided a housing which generally encloses the "rotor and which is formed to provide volutes or like means for receiving the separated underflow and overflow materials for discharge. Such rotor is provided with a lower conical impeller portion which has an axially disposed opening faced downwardly for receiving returned underflow material when such return is provided for, and usual means are provided for supplying feed to the centrifuge.

Centrifuges of this general type have found wide and successful application in a large variety of industrial processes such as the separation of starch from gluten or other thickeningand/or classifying operations. Despite the recognized success of such machines, those heretofore employed have suffered from one major inherent disadvantage in that they were incapable of operating under substantial pressure due to the fact that no mechanical seals are available which simultaneously seal the rotor housing against the escape of pressure and at the same time permit free rotation of the rotor .s'haft'while accommodating axial and radial misalignments of such shaft during operation. In this connection it is to be noted that radial and axial misalignment during movement of the shaft is to a certain degree inevitable due to the fact that temperature changes as well as conditions of unbal- "ance' due to material flow within the rotor housing contribute to significant shaft movement.

However, it has long been known that if suitable ways and means could be provided to seal suchcentrifuges while permitting free rotation of the shaft and accommodating axial and radial displacement thereof, an entire mew field for the application of such machines would be opened.

It is therefore the primary object of the present inven- :tion to provide acentrifuge capable of operating at elevated pressure.

A further object is to provide such a centrifuge having a particular type .and arrangement ofseal to accommodate axial and radial displacement of the shaft during op.eration :but yet providing for free rotation of such shaft to enable unimpaired operation of the centrifuge. .Another object .is to provide .sealing means for a cenh a n 'sern'bly.

' Suitable means are provided to control the infeed, discharge and return flows within the centrifuge itself in order to maintain proper operating. pressures therein.

2,917,228 Patented Dec. 15 1 959 "ice trifuge that is simple and economical of construction yet provides ready access to the shaft for maintenance.

Still a further object isto provide a complete closed system enabling the processing of materials in a centrifuge under elevated pressures.

In brief, the foregoing, and possibly other objects, are attained by this invention by the employment of ways and means which provide for a bearing and shaft seal mounted functionally remote from the interior of the rotor housing and in which the rotor shaft is journalled for rotation. Such bearings and seals are mounted to be movable with the shaft during axial or radial movement thereof thereby enabling shaft movement without impairing the mechanical efl'iciency'of the bearing ,or seal with which the shaft is associated.

In combination with such bearing and seal, the invention further provides means for sealing the rotor housing itself, such means comprising a housing enclosing such bearing and seal and movable therewith, and a flexible closure or coupling connecting such bearing housing with the rotor housing; There is thus provided an arrangement whereby aida l and radial movement of the rotor shaft with respect to the rotor housing is permit-ted while at the same time rotation of the shaft is unimpaired because the relative position of the shaft and bearings rcrnains unchanged. A seal for maintaining pressure within the rotor housing and at the same time to protect the bearings against the atmosphere of the rotor housing also moves with the shaft and is mounted to protect such bearings preferably by being positioned within the bearin g housing. A flexible coupling interconnecting the housing with the rotor housing completes the as- The foregoing and other morespecific objects of the invention will be readily apparent from a perusal of the following description of the accompanying drawings. It is to be understood that the description of the illustrated embodiment is for purposes of illustration only .and is not to be taken as limiting the invention, the scope of which is defined by the appended claims rather than by the description' preceding such claims.

' In thedrawings:

l is a side cross-sectional view partly in elevation illustrating a centrifuge incorporating the present invention. Y

Fig. '2 is an enlarged detail in section showing the flexible sealing means of the invention, certain elements being shown in elevation for purposes of clarity.

Figs. 3 through 8 are sectional views of the flexible sealing means of the device illustrating more or less schematically the rnannersin which radial and axial eccentric movement -is accommodated.

' Fig. '9 is a sectional view similar to the central portion of Fig. 2 illustrating the manner in which the flexible coupling seal iscollapsed to provide access to the shaft.

Fig. 10 is a diagrammatic flowsheet illustrating a pressured treating system embodying the pressured centrifuge of the present invention.

'Thecentrifuge illustrated in the drawings comprises generally a rotor 11 carried by a vertical shaft 12 and disposed within a stationary rotor housing 13. The machine "is provided with a feed passage 14, an overflow passage 16 for discharging a centrifugally separated lighter fraction, an underflow passage 17 for discharging a centrifugally separated underflow fraction, and a passage 1.8 for introducing ;a supplemental fluid material which may be heavier centrifugally separated discharge material or underflow. The rotor shaft 12 is connected coupling 19 to a vertical shaft 21 which is journalledfor rotation .lower end of rotor shaft 12.

in a bearing assembly 22 which is in turn housed in a flexibly mounted bearing housing 23, as more fully described hereinafter.

As is conventional, the rotor housing 13 can be conveniently formed of separable sections 13a, 13b and 130 of which section 13a forms a volute chamber 24 for receiving separated overflow, and section 13b is formed to provide a volute chamber 26 for receiving centrifugally separated heavier or underflow material.

The body of rotor 11 can likewise be formed from a number of separable parts, including, in the embodiment illustrated, a main part 11a and upper and lower conical shaped parts 11b and 11c respectively. The main part 11a has an inner structure 27 which is attached to the Parts 11a and 11b are retained together by suitable means such as an expansible clamping ring 28. Within the rotor 11 there is a separating chamber 29 in which is positioned a group or stack of separating discs 31 such as are commonly used in such centrifuges. Circumferentially spaced underflow discharge nozzles 32 are positioned on the outer peripheral wall 33 of main rotor portion 11a, each of such nozzles being provided with a discharge orifice directed backwardly with respect to the direction of rotation of rotor 11. The annular peripheral portion of rotor main part 11a is accommodated within a diverging portion 36 or throat ring of rotor housing part 13b.

As is described in US. Patent 2,625,321 the lower portion 110 of the rotor forms an impeller for the return of centrifugally separated underflow material back into the rotor, thus the lower end of rotor part 110 is provided with an axially and downwardly faced opening 18 positioned directly above a nozzle 38 in turn positioned on the lower part of housing 13. Such nozzle directs a jet or solid stream of returned underflow material upwardly into the impeller. Opening 18 is positioned or formed in a ring 39 removably mounted on the lower end of rotor part 11c.

Within such impeller, material is acted upon by radially extending vertical webs or vanes 41 which serve to impart rotational velocity to the material. Such material passes through spaces between webs 41 then outwardly through return tubes or passages 42 to pass through main separating chamber 29 which communicates with discharge nozzles 32.

Lower portion 130 of the rotor housing is conical shaped conforming generally to the contour of the lower part of rotor 11. In this manner it is insured that spilled fluid material, in the absence of extraneous forces, tends to collect in the lower part of such housing adjacent the lower end ofthe rotor.

Means, such as disclosed in US. Patent 2,559,453, are employed to return spilled material from the lower end of the housing into the stream of returned underflow material. Preferably, as disclosed in such patent, an aspirating device is employed to accomplish such return and operates to return the spilled material by merging the same with the upwardly discharging jet issuing from nozzle 38. Briefly, such aspirating means comprises an annular contour member 46 mounted immediately over nozzle 38 in such a manner that an upwardly extending conical shaped portion 47 forms an upper opening 48 of a diameter only slightly larger than the concentric orifice opening 49. Member 46 is provided with a skirt 51 which extends outwardly and is held in position by suitable screws or bolts 52 in conjunction with spacers 53 to thereby form a passage 54 between member 46 and the adjacent surface of nozzle 38. An outer peripheral inlet portion 56 of passage 54 is adapted to receive spilled material so that when during operation the jet of material discharging upwardly from nozzle orifice 49 induces flow through passage 54 by virtue of aspirating action thus drawing material through passage 54 from inlet 56 to merge the same with the upwardly discharging jet.

To prevent undesirable swirling movement of spilled and collected material and thereby insure an even flow of such material into passage 54 there is provided in the lower part of the housing a plurality of baflies or vanes 57. Such vanes are mounted in suitable manner on the wall of rotor housing portion and extend substantially the entire height thereof. Such vanes operate in the manner disclosed in US. Patent 2,625,321 and, as noted above, prevent swirling of spilled material.

As can be best seen from Fig. l, a centrifuge of the type under discussion is supported for rotation only adjacent its upper end (bearing assembly 22 in bearing housing 23). Consequently the shaft may be subjected to eccentric non-rotational movement due either to temperature changes or material unbalance within the rotor. In order to protect the bearing assembly from the deleterious effects of material undergoing separation within the rotor it is highly desirable that such hearing be spaced from the rotor housing.- In the usual installation as heretofore employed where substantially atmospheric pressure only is maintained within the rotor housing no difiiculty has been experienced in this regard and sealing of the shaft passage 58 in housing cover 59 has been readily accomplished by means of any suitable vapor seal or gasket which serves to minimize vapor leakage.

However, such seals are not suitable for high pressure operation because they cannot accommodate eccentric movement of the shaft and at the same time maintain an adequate pressure-tight seal over long periods of operation. We have discovered that an adequate as well as economical and eflicient seal can be provided without substantial structural modification by the use of a particular combination of elements including flexible mounting means for the bearing housing and a flexible coupling generally designated 61 interconnecting the bearing housing and the rotor housing cover. A suitable linear hydraulic seal of conventional design is mounted on shaft 21 between such bearing assembly 22 and the rotor housing 13.

Such an arrangement is illustrated in Figs. 2 through 9 in which it will be noted that the bearing housing 23, which is restrained from upward movement by shafts 62 is flexibly mounted by springs 63 and shock absorbing mounts 64 to thereby permit such housing to tilt or otherwise move with eccentric movement of shaft 21.

As previously noted, a shaft seal 66 is mounted on shaft 21 and bearing housing 23 in such a manner that it moves whenever the shaft and bearing housing move during eccentric movement of the shaft, thus no undue strain is placed upon the bearing during such eccentric movement, consequently it cannot bind or wear to a greater extent than would normally be expected with a completely fixed shaft. Such a seal may be any one of a number of seals specifically made for such purpose, and may for example be a model ROTT/ROTT double face type mechanical seal manufactured by the Durametallic Corporation of Kalamazoo, Michigan.

To provide a seal between the flexibly mounted bearing housing and the stationary rotor housing 13 there is provided, in accordance with this invention, a flexible coupling 61 capable of accommodating both axial and radial movement while at the same time maintaining a seal against the escape of pressure existing within housing 13.

Such coupling in the embodiment illustrated comprises a central portion or sleeve 67 having outwardly turned annular flange sections 68 adjacent both ends, and a pair of oppositely aligned cylindrical sections or sleeves 69 each having an inwardly turned annular flange section 71. As is seen in the drawings, outwardly turned flanges 68 are overlapping with respect to inwardly turned flanges 71 thus providing a more or less continuous conduit or coupling 61, the respective parts of which are slideable or movable relative to each other.

In order to provide sealing between the overlapping parts, 0 rings 72 are employed which sealingly engage the outer wall 73 of cylindrical section 67 and simultaneously sealingly engage the inner wall 74 of each end cylindrical member 69. As best shown in Figs. -3 through 8, this arrangement permits normal operation (Fig. '3), accommodates axial displacement such as may :occur due to temperature changes (-Fig. 4), accommodates radial misalignment or shifting (Fig. 5) or tilting (Fig. 6) or combinations of lateral shifting and/or tilting along with axial displacement (Figs. 7 and '8 It will be noted that the 0 rings are constantly in engagement with the outerand inner walls 73 and 74 of the cylindrical members :67 and :69. Thus, regardless of the relative positions of bearing housing 23 and rotor housing 13 a seal is constantly maintained. In this connection it will be noted that there is provided beveled portions 76 on each of the flange members 68 and 71 which permit greater movement of the respective parts of the coupling yet at the same time prevent direct contact between such parts since the bevel accommodates such movement and provides space-to prevent such contact. -At all times the 0 rings provide the seals while the flanges serve to hold "the 0 rings in position and maintain the coupling as a unit. 3

As shown in the drawings, central section 67 of coupling 61 is desirably formed from two separate sections or sleeve members 77 which are suitably bolted together as by bolt 78. This enables ready assembly of the coupling and also permits replacement of any defective parts.

A further distinct feature of the embodiment illustrated lies in its ability to be collapsed to provide ready access to shaft coupling 19 for inspection or for dismantling. This is best illustrated in Fig. 9 which shows how bolts 79 (see Fig. 2) are removable to allow upper section 69 and central section 67 to collapse or telescope downwardly to completely expose shaft coupling 19.

As is usual in constructions of the nature under discussion, bearing oil may be supplied to the bearing assembly 22 in conventional manner and is drained out through conduit 81. Sealing fluid under pressure may be supplied to shaft seal 66 via conduit 82, and discharged therefrom via conduit 83. I

Where required, other 0 rings or similar stationary seals 84 are employed in known fashion to insure against leakage at rigid joints.

Although the invention has been described with particular reference to a centrifuge in which the rotor shaft is journalled at the upper end only, it is to be understood that it may be used with machines in which the shaft is journalled at the lower end, or at both ends, since the essential combination of the flexibly mounted bearing housing and interconnecting flexible coupling between such housing and the rotor housing may be employed in any of such embodiments.

Fig. is a fiowsheet of a system embodying a pressured centrifuge. In such fiowsheet a centrifuge, generally indicated at 85, is employed for the separation of a solid such as a catalyst from a liquid under pressure. Such centrifuge, which may be of the type previously described, is driven in conventional manner by means of drive pulley 86, V belts 87 and a motor 88. A pressured sealing liquid such as required by seal 66 (Fig. 2) is supplied from a suitable source of supply 89 under pressure by a pump 91 from which it is delivered via suitable conduit 82 into the seal and subsequently discharged via the discharge conduit 83. In the embodiment illustrated the flexibly mounted bearing housing 23 is connected to the centrifuge by means of a flexible coupling 61.

Material to be treated is supplied by pump 92 and con duit 93 into a pressured feed tank 94 from which it is delivered by means of pump 96 and valved conduit 97 to the centrifuge where it enters through a feed inlet 98 (Fig. l) and is subsequently separated. Overflow material is discharged via a conduit 99, which may be suitably valved, into a pressured overflow tank 101 from which it is subsequently discharged via a valved conduit 102 to further process or other use. Underflow material is discharged via a valved conduit 103 and, if desired, pump 104 into a pressured underflow receiver tank 105 from which it is subsequently discharged at a controlled rate by means of a valved discharge conduit 106. A bypass conduit 107 is employed to divert a portion of the under-flow material for recycle to the centrir fuge. Valved conduit 1'08 and pump 109 are provided to permit the addition of a wash liquid into the system.

By means of the pressured feed supply tank 94, pressured overflow receiver 101 and underflow receiver 105 constant pressure may be maintained on the liquids entering and leaving the centrifuge. In order to insure equalization of pressures particularly vapor pressures in .all such receptacles and in the centrifuge itself, vapor equalization lines 111, 1 12, 113and 114 interconnecting respectively the overflow receptacle and feed tank, the rotor housing and feed tank, and the underfiow receptacle and feed tank, are provided.

In order to insure against pressure loss through the shaftseal 66, the sealing liquid is maintained under a pressure slightly greater than the pressure in the rotor housing. For instance, in the manufacture .of polyethylene, it is necessary to remove a granular catalyst from a viscous hydrocarbon stream, and for process reasons the separation must be carried out at elevated pressures in the range of about 90 to p.s.i.g. In carrying out such separation in a centrifuge embodying the present invention, suitable pressures were maintained in the centrifuge by the system described with reference to Fig. 10 and a pressure in the shaft seal of about p.s.i.g. was maintained. Thus, if any leakage occurred in such seal, it would result in a negligible amount of sealing liquid entering the rotor housing rather than the rotor atmosphere entering the bearing assembly.

We claim:

1. In combination with a centrifuge of the type including a rotor housing, a rotor vertically disposed in said housing and mounted on one end of a substantially vertical shaft extending upwardly through an opening in said rotor housing, and a flexibly mounted bearing assembly mounted outside of said housing and upwardly spaced from said rotor housing opening, said shaft being journaled for rotation in said bearing assembly; a pressure sealing assembly comprising means sealing said bearing assembly against the ingress of pressured atmosphere, and a pressure resistant flexible coupling connected at one end in sealing relationship with said bearing assembly and at its other end in sealing relationship with said rotor housing aroundsaid rotor housing opening, said flexible coupling being made of pressure resistant material and comprising a first rigid cylindrical member having an annular flange on each of its opposite ends, second and third rigid cylindrical members substantially identical to each other and concentrically positioned about opposite ends of said first member in sliding relationship therewith thereby enabling independent movement of each of said members relative to the others, each of said second and third members having an annular flange at one end thereof in overlapping relationship with the flange of said first member, and compressible gasket-like members between said overlapping flanges in simultaneous sealing engagement with the walls of said first member and the walls of said second and third members.

2. In a centrifuge having a fixed housing, a rigid vertical shaft extending through a top opening in said housing, said shaft having a rotor rigidly attached to its lower end portion within said housing and having its upper end portion journalled in a yieldably mounted bearing assembly spaced upwardly from said housing to thereby enable rotational as well as radial and axial movement of said shaft and rotor with respect to said fixed housing; the improvement enabling maintenance of a pressured atmosphere within said fixed housing independent of pressure 'conditions within said bearing assembly, said improvement comp-rising a flexible gas seal concentrically surrounding said shaft and connecting said fixed housing with said yieldable bearing assembly, said flexible gas seal comprising a plurality of axially aligned cylindrical sleeves including an upper sleeve having an inwardly extending annular flange at its lower end and rigidly secured at its upper end to the bottom of said yieldable bearing assembly, a lower sleeve having an inwardly extending annular flange at its upper end and rigidly secured at its lower end to said fixed housing, an intermediate sleeve provided with an outwardly extending annular flange at each of its ends and having said ends positioned concentrically within the flanged ends of said upper and lower sleeves with said outwardly extending flanges in overlapping relationship with said inwardly extending flanges, compressible O-ring members contained between said overlapping flanges in the space between the walls of said concentric sleeves, and a shaft seal rigidly mounted on said yieldable bearing assembly within said upper sleeve thereby sealing said bearing assembly against pressures within said fixed housing and said flexible gas seal.

3. Apparatus according to'claim 2 inwhich the termi= nal edges of said inwardly and outwardly extending flanges are rounded whereby metal to metal contact of said cylindrical sleeves is prevented in all operating positions of said cylindrical sleeves.

4. A centrifuge according to claim 2 in which said termediate sleeve comprises two'sleeve members each having an outwardly extending annular flange at one end and an inwardly extending annular flange at the other end, and said two members are secured together wtih said inwardly extending flanges in face to face 'relationship.

References Cited in the file of this patent UNITED STATES PATENTS 1,561,784 Hall Nov. 17, 1925 1,945,786 Peltzer Feb. 6, 1934 2,210,054 Andersson Aug. 6, 1940 2,532,773 Kellam Dec. 5, 1950 2,668,658 Peltzer Feb. 9, 1954 2,779,536 Pomeroy Ian. 29, 1957

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