US2985361A

US2985361A - Centrifuge

Info

Publication number: US2985361A
Application number: US653930A
Authority: US
Inventors: Frederick H Smith
Original assignee: Sharples Corp
Current assignee: Sharples Corp
Priority date: 1957-04-19
Filing date: 1957-04-19
Publication date: 1961-05-23
Anticipated expiration: 1978-05-23

Description

y 23, 1961 F. H. SMITH 2,985,361

CENTRIFUGE Filed April 19, 1957 4 Sheets-Sheet 1 9 22 56 Q a I I8 39 3a 2a 40 INVENTOR. FRE DERICK H. SMITH BY/g'am ATTORNEY F. H. SMITH CENTRIFUGE May 23, 1961 4 Sheets-Sheet 2 Filed April 19, 1957 INVENTOR. FREDERICK H. SMITH BY W 0% i ATTORNEY May 23, 1961 F. H. SMITH 2,935,361

CENTRIFUGE Filed April 19, 1957 4 Sheets-Sheet 3 Ill IN VEN TOR. FREDERICK H. SMITH BY M aw ATTORNEY F. H. SMITH CENTRIFUGE May 23, 1961 4 Sheets-Sheet 4 Filed April 19, 1957 INVENTOR. K H.

F REDERIC SMITH ATTORNEY tates CENTRIFUGE Frederick H. Smith, Huntingdon Valley, Pa., assignor to The Sharples Corporation, a corporation of Delaware Filed Apr. 19, 1957, Ser. No. 653,930

3 Claims. (Cl. 233-45) This invention relates generally to centrifuges for separating materials of different densities such as centrifugal separators and centrifugal clarifiers, and more particularly this invention relates to centrifuges in which the materials to be separated or clarified are introduced or fed into the rotating rotor or bowl of the centrifuges under pressure.

The liquid materials fed to centrifuges for separation or clarification frequently are accompanied by substantial quantities of gas or vapor, hereinafter for convenience referred to collectively as gas. The gas may be coarsely or finely dispersed in the flowing liquid or there may be an alternate how of what are commonly referred to as slugs of liquid separated by gas.

The gas may be air which has been entrained in the liquid to be centrifuged by agitating in an open container prior to pumping it to a centrifuge. For example, in the refining of vegetable oil to wash soap out of the oil, the oil may be agitated with water in an open tank. The soap dissolves in the water, and the mixture is passed to a centrifuge to separate the oil freed of its soap and the soapy water. Agitation which is sufiicient to result in a satisfactory transfer of the soap from the oil to the water results in an .occlusion of air in the mixture which is carried on to the centrifuge.

As another illustration, the gas may be the result of a reaction between constituents of the liquid material to be centrifuged. For example, crude vegetable oil containing fatty acids may be treated with a solution of sodium carbonate for neutralization of the acids. The sodium carbonate reacts with the fatty acids forming soaps and liberating carbon dioxide. The mixture containing dispersed gaseous carbon dioxide and insoluble soap, is fed to a centrifuge to separate the soap from the neutralized oil.

Frequently a liquid mixture to be separated is heated, for instance to reduce its viscosity to facilitate separalion, such as by heated surfaces or by the introduction of vapors as it is passed to a centrifuge, with the result that the liquid contains free vapor, that is gas when it enters the centrifuge.

On the other hand, a leaky stuffing box or pipe connection on the inlet side of a pump used for feeding a liquid mixture to a centrifuge may allow air to leak into the mixture fed to the centrifuge.

Then too, the gas in the mixture fed to the centrifuge may be the result of incomplete solution or incomplete reaction of a gaseous reagent admixed with a feed to the centrifuge as, for instance, in case of the addition of gaseous ammonia to neutralize, and form insoluble soaps with, the fatty acids contained in vegetable oil.

Even though the liquid to be centrifuged contains no gas, conduits leading from the supply of liquid to be centrifuged may be full of gas which is displaced by the initial flow of liquid and is conducted to the centrifuge.

Irrespective of the origin of gas which occurs with the liquid fed to a centrifuge, or the nature of such atent gas, when such mixtures are fed to a centrifuge under pressure with sealed feeding connections, such as a centrifuge of the full bowl type, the gas is forced into the bowl of the centrifuge. As will be seen from a study of the details of the design of such a centrifuge hereinafter described, gas introduced with the liquid feed accumulates in the bowl of the centrifuge, greatly interfering with its effectiveness as a separator or clarifier. and greatly increasing the amount of pressure required to force the liquid to be centrifuged through the centrifuge, unless provisions are made for the release from the bowl of such gas.

In the case of cream separators of the full bowl type, there has been a ready solution. A passage has been provided connecting all parts of the center of the bowl so that any gas entering the bowl may pass from one compartment to another, and out of the bowl with the separated cream. However such a passageway, if large enough to satisfactorily relieve any accumulation of gas, also permits the passage of unseparated liquid entering the centrifuge bowl which becomes mixed with the discharging cream. This can be tolerated in the case of cream separation since cream is merely a concentration of butterfat particles in milk serum, and a minor dilution of concentrated cream with the whole milk fed to the centrifuge can be compensated for by effecting somewhat higher concentration of cream in the main separating compartment of the bowl. I

The above-mentioned passageway is not a solution to the problem when the full bowl type of centrifuge with sealed feed is used in separations where it is desired to have the lighter component of the mixture discharged from the bowl unpolluted by the feed to the bowl, as, for instance, in the separation of oil from water containing dissolved soap, or in the separation of oil from soapstock, as has been referred to above, or in the separation of neat soap from nigre in the manufacture of soap. In such cases the passageway in the center of the bowl for the release of gas would allow the pollution of the separated lighter liquid component of the mixture with gas and liquid of the feed which had not passed through the effective separating devices of the bowl.

The pollution of the separated lighter liquid component is exceptionally objectionable in the case of the separation of neat soap from nigre. In that case the shearing of the air and neat soap mixture, which occurs as the mixture passes from the rapidly rotating bowl to the stationary receiver, results in a very fine dispersion of the air in the neat soap. This air can only be separated from the neat soap by very prolonged settling at high temperature.

This invention provides a practicable and effective means for the release of gas entrapped in centrifuges fed under pressure and provided with sealed feed arrangements, without (1) the disadvantage of pollution of the lighter separated component with other components fed to the centrifuge, without (2) reduction of effectiveness of the operation of the centrifuge bowl, and without (3) imposing an increased resistance to the feed of material to the centrifuge bowl.

Further features of the invention will become apparent to persons skilled in the art as the specification proceeds and upon reference to the drawings in which Figure 1 is an elevation, partly in section, illustrating one form of the invention;

Figure 2 is a perspective view, partly in section, of the form of the invention shown in Figure 1;

Figure 3 is a sectional elevation, shown broken, of another form of the invention; and

Figure 4 is a sectional elevation, shown broken, of a further form of the invention.

Referring now to Figure 1, the lower part of a centrifugal separator bowl, together with associated parts, is shown in section. The bowl shell 10 is surmounted by a bowl top (not shown) which is held on to the bowl shell 10 by the coupling ring 11 threadedly connected to the bowl shell Hi. The bowl shell 10 is mounted on the bowl spindle 12 and held in place thereon by the nut 13 which is threadedly connected to the bowl spindle 12. The bowl spindle '12 is mounted in a conventional manner for the rotation of the bowl and the bowl spindle. The disc stack support 14 rests on the bottom of the bowl shell 10 and is held in contact therewith by engagement with the bowl top (not shown). The disc stack support 14 is held in concentric relationship to the bowl shell by the cylindrical contact 15 between the shoulder on the bowl shell 10'and the shoulder on the disc stack support 14 and also the engagement of the upper end of the disc stack support 14 with the bowl top (not shown). A slot 17 in the internally projecting flange 18 of the disc stack support 14 is adapted to fit over the pin 19 fixed in the bowl shell 19 to orient the disc stack support 14 with respect to the bowl shell 10.

A disc stack 22 which is shown for convenience as of a conventional type, is located in the main separating chamber 21 of the bowl between the lower conical skirt of the disc stack support 14 and the bowl top (not shown). The vertical spacing of the disc is accomplished by any suitable means such as by means of spacers 23 fastened to the upper surfaces of the discs to form thin separating spaces between the discs.

The bowl is mounted to rotate within the frame 24 to which is attached the cover 25 by a plurality of screws 26 of which only one is shown. Cover 25 in turn supports an assembly of parts for collecting the separated products discharging from the bowl, for example, as shown in Figure 5 of US. Patent 2,717,119, dated September 6, 1955.

The bowl spindle 12 is tubular and has a concentric channel 28 throughout its length. The lower end of the bowl spindle 12 is adapted to rotate in well-known sealing means between it and a stationary conduit by which the materials to be separated are fed to the centrifuge, a preferred form of which is shown in Figure 6 of said US. Patent 2,717,119. The nut 13 is provided with a number of radial holes 31 communicating with the channel 28 in the spindle and also with feed distribution chamber 32 which has a closed top and is located between the bottom of the bowl shell 10 and the conical skirt 20 of the disc stack support'14. Integral or associated with the conical skirt 20 of the disc stack support 14 are a number of accelerating radial wings 33.

Each of the discs of the disc stack 22 is provided with a plurality of circumferentially spaced holes 34 positioned between its inner and outer edges, and these holes are arranged one above the other in the disc stack 22 to form vertical channels 35 (only one being shown) extending through the vertical length of the disc stack 22. The conical skirt 20 of the disc stack support 14 is provided with a number of tubular passages 36 positioned radially outwardly from the axis of rotation, each passage 36 communicating at one end with the feeddistribution chamber 32 below radial holes 31 and at the other end with a separate vertical channel 35.

In accordance with the embodiment shown in Figures 1 and 2, an axially positioned hole 37 is provided in the top of the nut 13. A gas vent tube or conduit 38 passes through the axial hole 37 in the nut 13, downward through the axial channel 28 in the bowl spindle 12 turns a right angle and passes radially through a hole 40 in the side wall of the bowl spindle 12, and is arranged in liquid tight connection therewith. Thus the gas vent tube 38 provides an open passage from the top center of the feed distribution chamber 32 above radial holes or feed inlet 31 to the exterior of the bowl'spindle 12 with a part thereof disposed radially. Any other similar form of gas vent passage may be substituted.

In operation for the separationof feed liquidinto separate parts, the feed liquid is .fed to the centrifuge and upwardly through the channel 28 in the bowl spindle 12, and radially outward through the holes 31 in the nut 13 into feed distribution chamber 32. In this space the accelerating wings 33 accelerate said feed liquid to the angular rate of rotation of the bowl. The feed liquid then passes through the passages 36 and upwardly through the vertical channels 35 in the disc stack 22, and then into the thin spaces between the discs. In the thin stratified layers between the discs eifective separation of the liquid components takes place under the influence of centrifugal force. The lighter liquid component moves toward the axis along the upper surface of the individual discs into the annular channel 41, and ultimately out of the centrifuge in a conventional or other manner. The heavier liquid component moves away from the axis of the bowl along the lower surface of the individual discs into the annular channel 42, and finally out of the top of the bowl, also in a conventional or other manner.

In view of the large difference in density between gas and liquid fed to the centrifuge, and the correspondingly greater ease of separation of gas from liquid than the separation of liquid components from each other, gas fed to the centrifuge along with the liquid mixture rapidly separates in feed distribution chamber 32, forming a cylindrical core of gas surrounded by liquid. In the absence of this invention, the gas accumulates until it reaches the outlet of the tubular passages 36, and then any further gas fed to the centrifuge passes up into the disc stack, rapidly. passing toward the axis in the lower discs, and creating a turbulence in that portion of the bowl which greatly impairs separation. Incoming liquid is slungoutwardly and through this gas space hitting the liquid layer in the bowl with an impact which increases the intimate intermixture of the liquids fed to the bowl, and making more difficult their final separation. Above the conical skirt 20 of the disc stack support 14, the liquid layer extends to the axis of the bowl and exerts a high back pressure on the gas trapped beneath the conical skirt 20 of the disc stack support 14, and, in some instances, as much as pounds per'square inch additional pressure may be required to feed liquid into a bowl of conventional size and speed when gas is so trapped in the bowl.

In a conventional bowl, a passageway is provided from an axial position of the feed distribution chamber 32 through the disc stack support 14 to the annular channel 41. All of the gas which is in such a state of aggregation that can be separated in the feed distribution chamber 32 flows through this passageway together with a part of the liquid mixture fed to the centrifuge. Both the gas and this portion of the liquid feed mixture are picked up by the discharging stream or separated lighter component flowin gthrough the annular channel 41, and are discharged together therewith at the top of the centrifuge bowl. With this conventional method of releasing the gas which is separated beneath the conical skirt 20 of the disc stack support 14, the lighter liquid component which has been eifectively separated in the disc stack is polluted with both the gas and a portion of the feed liquid. The rotating stream discharging from the rotating centrifuge bowl into the non-rotating receiver is subjected to intense shear with the result that the polluting gas and feed liquid is intimately intermixed with the pure lighter liquid component. Even in those cases as in the separation of neat soap from nigre where a slight pollution of the neat soap with a portion of nigre may be tolerated, the subsequent separation of the very finely divided air from the viscous neat soap is accomplished only with considerable difficulty.

In accordance with this invention gas which is separated in the feed distribution chamber 32 beneath the conical skirt 20 of the disc stack support 14 is forced to the axis of rotation of this space by centrifugal force, and passes out of the bowl through the gas vent tube 38,-and from its external discharge opening 39 on the side of the; spindle into the space below the owl, centrifugal force in the radial portion of the gas vent tube 38 assisting in this flow. Some of the liquid fed to the centrifuge may also pass from the feed distribution chamber 32 through the gas vent tube 38, but this may be tolerated for it does not interfere with the separation.

Resistance to the feed of mixtures to the centrifuge by reason of accumulation of gas in the bowl is thus avoided. Reduction in the separating effectiveness of the disc stack by gas passing through the disc stack also is avoided. Pollution of the separated lighter liquid component by gaseous or liquid mixtures fed to the bowl also is avoided.

The gas and liquid mixtures discharging from the side of the spindle into the space 47 may be collected. The liquid thus discharged which is but a small portion of the total liquid fed to the centrifuge may, after separation as by gravity from the gas, be re-fed to the centrifuge.

Referring now ot Figure 2 there is shown in perspective a sectional view on a larger scale of the bottom of the bowl shell the bowl spindle 12, the disc stack support 14 and the gas vent tube 38 of the invention. In this figure as compared with Figure 1 like reference numerals are used throughout to designate like parts.

A modification embodying the invention is illustrated in Figure 3 in which there is shown, as in Figure l, the bowl shell 10 and the bowl spindle 12. The gas vent tube 51 terminates flush with the upper end of the bowl spindle 12 to reduce the danger of damage to the end of the gas vent tube 51 when the bowl is removed from the spindle as for cleaning. The gas vent tube 51 is supported at its upper end centrally in the bowl spindle 12 by a plurality of radial fins 53 which may be made an integral part of gas vent tube 51 as by welding. The lower end of the gas vent tube 51 is fitted such as with a force fit in the hole 54 in the side of the bowl spindle 12 resulting in a substantially liquid tight joint. An auxiliary gas vent tube 55 is inserted such as with a press fit in a central axial hole in the nut 52, and thereby may be made an integral part thereof. The lower end of the auxiliary vent tube 55 surrounds the upper end of the gas vent tube 51, and serves to conduct gas separated in the feed distribution chamber 32 to the gas vent tube 5-1.

A vent hole 56 in the nut 52 permits the escape into the feed distribution chamber 32 above the nut of any gas which may be trapped under centrifugal force within the nut 52 or the bowl spindle 12.

As determined by the requirements of manufacture and strength, the gas vent tube 51 may be of such dimensions as to carry out of the bowl not only all of the gas which may be fed to the bowl, but also an undesirably large proportion of the liquid feed. In such instances, the rate of flow may be controlled by a bushing 57 with an orifice of predetermined size to give a desired rate of flow. Bushing 57 is shown pressed into the upper end of the gas vent tube 51.

A further modification embodying the invention is illustrated in Figure 4. As in Figure 3 the gas vent tube 51 is sealed at its lower end into the hole 54 in the side of the bowl spindle 12 and is supported at its upper end by the radial vanes 53- centrally in the bowl spindle 12. A gas vent tube extension 61 is fitted about the upper end of gas vent tube 51 in liquid tight relationship as by a press fit. Near the upper end of the gas vent tube extension 61 is a circumferential groove 62. A plurality of radial holes 63 extend from this groove to the axis and an axial hole 64 provides a passageway from the radial holes 63 out through the bottom of vent tube extension 61 into the gas vent tube 51. The internally extending flange 65 of the nut 66 which holds the bowl shell 10 on to the bowl spindle 12 surrounds the upper end of the gas vent tube extension 61 and is provided with an annular groove 67 in the same plane as the annular groove 62 on the vent tube extension 61. A ring 68 preferably of circular cross section and of resilient material, as for instance rubber, fits into the annular groove 62, normally sealing off the outer ends of the radial holes 63.

When the bowl is rotated at operating speed the resil ient ring 68 is expanded by centrifugal force into the annular groove 67. The clearance between the extension 61 and the nut 66 is such that the resilient ring 68 cannot escape from the annular space defined by the annular grooves 62 and 67, but gas fed to the centrifuge may freely pass from either the space above or below the internally extending flange 65 of the nut 66 into the radial holes 63, and eventually out through the side of the bowl spindle. The ring 68 having been selected of a density somewhat less than that of the lighter liquid component of the liquid mixture fed to the centrifuge, when gas has escaped from the space above and below the inwardly extending flange 65 of the nut 66 and liquid enters the annular grooves 67 and 62 the ring 68 floats upon the liquid and is forced inwardly sealing off the radial holes 63 and preventing escape of liquid through the gas vent tube. A further occurrence of gas displacing the liquid in the annular grooves 62 and 67 reopens the radial holes 63.

A vent hole 69 from the outermost portion of annular groove 67 directed away from the axis and opening into the feed distribution space 32 prevents trapping of liquid under centrifugal force in annular groove 67.

While for the purpose of convenience the invention has been described in connection with a particular type of centrifugal separator bowl, it may advantageously be used with other types of centrifugal bowls whether adapted for separation of liquids, their clarification or otherwise, as for example, centrifugal clarifier bowls for the separation of non-liquid or solid particles from a liquid.

The vertical channels extending through the disk stack may be closer to or farther away from the outer edges of the discs, or, and particularly in the case of clarifier bowls, they may be omitted entirely, these and other modifications being well known to those skilled in the art. Also, and particularly in the case of clarifier bowls, the conical skirt of the disc stack support may be so modified, such as in well known manner, that the liquid flowing through the centrifugal bowl is fed directly from the feed distribution chamber to the annular channel 42 surrounding the discs. Furthermore while I have described the invention as applied to centrifugal bowls provided with discs for the accelerating and decelerating of the liquid as it flows radially outwardly and inwardly, respectively, within the bowl, and for the stratifying of the liquid into thin layers, other types of acceleratingdecelerating devices may be used, for example, the main separating chamber 21 may be provided with the well known wing type of accelerating-decelerating device as illustrated in U.S. Patent 1,401,196, or the spiral blade type of accelerating-decelerating device as illustrated in U.S. Patent 2,138,468. There is also shown in these patents means for distributing the feed. Combinations of various types of accelerating-decelerating devices also may be employed, such as those known in the art.

Having more particularly described my invention, it is to be understood that this is by way of illustration and not by way of limitation, and that modifications may be made without departing from the spirit of the invention. Thus while my invention has been more particularly described in connection with a bowl adapted to be rotated about a vertical axis, it will be understood that my invention is similarly adaptable to a bowl rotating about any other axis, such as a horizontal axis.

Other modifications will occur to persons skilled in the art upon becoming familiar herewith. Accordingly, it is intended that the patent shall cover, by suitable expression in the claims, the various features of patentable novelty residing in the invention.

I claim: 1

l. The combination with a centrifuge bowl having a feed distribution chamber in its bottom, an inlet to said chamber positioned axially of said bowl adjacent to the top of saidchamber, and outlet means leading outwardly from said chamber from an area positioned below said inlet and outwardly from the axis of rotation of said bowl, of a spindle for said bowl having a feed channel leading to said inlet, and tubular means communicating with said chamber axially of said bowl above said inlet, said tubular means extending downwardly in said channel and then outwardly from the axis of rotation to an outlet in said spindle positioned below the bottom of said bowl.

2. The combination of claim 1 having means associated with said tubular means for controlling flow therethrough.

3. The combination with a centrifuge bowl having a feed distribution chamber in its bottom, an inlet to said chamber positioned axially of said bowl adjacent to the top of said chamber, and outlet means leading outwardly from said chamber from an area positioned below said inlet and outwardly from the axis of rotation of said bowl, of a spindlefor said bowl having a feed channel leading to said inlet, tubular means communicating with said chamber axially of said bowl above said inlet, said tubular means extending downwardly in said channel and then "outwardly from the axis of rotation to an outlet in said spindle positioned below the bottom of said bowl, and valve means in said feed distribution chamber associated with said tubular means, said valve means being adapted to open under the influence of centrifugal force when surrounded by gas and to close by flotation when surrounded by liquid.

References Cited in the file of this patent UNITED STATES PATENTS 416,320 Bergner Dec. 3, 1889 2,214,831 Hall Sept. 17, 1940 2,417,747 Flowers Mar. 18, 1947 2,717,119 Jones Sept. 6, 1955 FOREIGN PATENTS 114,253' Sweden 11113012, 1945