US1320419A - Centrifugal separator - Google Patents

Description

Patented Nov. 4, 1919.

mentor a; 197mm PHILIP T. SHARPLES, or s'r. DAVIDS, rENNsYLvANIA.

CENTRIFUGAL SEPARATOR.

Specification of Letters Patent.

Patented Nov. 4, 31919.

Application filed October 29, 1918. Serial No. 266,097.

To all whom it may concern:

Be it known that I, PHILIP T. SHARPLns, a citizen of the United States, and a resident of St. Davids, in the county of Delaware and State of Pennsylvania, have invented certain Improvements in Centrifugal Separators, of which the following is a specification.

Ihis invention comprises improved means for separating substances of difierent specific gravities with high efliciency throughout variations in the" amounts discharged, the relative volumes, and the viscosities of the constitutents to be separated. At the same time my invention makes it possible to construct a centrifugal machine in accordance with mathematical formulas to function in a predetermined manner.

In the design of a centrifugal separator there are two considerations of prime importance to be taken into account. After the constituents have been separated into respective layers within the rotor, it is usually necessary that the constituents be discharged separately, and that each constituent as discharged be as free from the other as in the centrifugal rotor. (2.) In order to gain high efficiency, each constituent should be subjected to centrifugal force for a period of time, the extent of which is dependent upon the resistance of the other constituent to separation therefrom and upon the specific results which it is desirable to effect; In the case of a mixture of constituents A and B, the primary object of the separation procedure is to get the A phase as free as possible from B, and the secondary object is to get the B phase as free as possible from A. If the separation of the B from the A phase is more difficult to accomplish than the separation of the A from the B phase, then the phase should be subjected to the separating force for a much longer period than the B phase. But, conversely, if the separation of the B from the A phase is very easily accomplished, both objects of the procedure'can be more nearly attained by sub ectmg the B phase to centrifugal force for a somewhat longer period than the Aphase,

lIn practice the period of time durlng which centrifugal force acts on a substance is dependent upon the amount of the substance held in the rotor, and the rate of displacement-r41. c.the rate of feeding and discharge. It is apparent, therefore, that ,the period of time during which each convolumes of the constituents held in the rotor. Obviously the relative amounts of the constituents held in therotor are not in any Way dependent upon the rates of discharge. The ratio between the amounts of the constituentsheld in the rotor is limited both for maximum and minimum by the mechanical considerations necessary to effect separate discharge.

Qnly by properly taking into account the points discussed above can a rotor be designed to function properly (to yield desired results at the maximum rate of displacement) for satisfactorily "handling the largest volume of material in a given time.

'Any means for insuring a correct ratio of the amounts of constituents in the rotor will insure at the same time correct functioning. The determination of just what is the correctratio for any given case can be gained by a consideration of the relative amounts of the constituents in the substance to be centrifugated, but an accurate determination is necessarily empirical. When the ratio has been determined, it, is

necessary to know how to construct a centrifugal rotor that will so function as to maintain this ratio.

Heretofore, it has been practicable to design centrifugal rotors to yield a given ratio of constituents held in the rotor for a given capacity (rate of combined discharge), a given ratio of amounts discharged, and a given viscosity of constituents. The formulation of this design, although somewhat dependent upon relative specific gravities of the constituents, has been in'the main purely empirical. It has been characteristic of all centrifugal rotors designed heretofore that the ratio of constituents held in the rotor has been decidedly altered by a change in capacity, a change in the relative rates of discharge, or a change in the viscosity of the constituents. The aforesaid variation in ratio has frequentlybeen so great as to go beyond the limitsrequired for the'separate discharge of constituents. For example, a rotor designed to maintain a correct ratio when two constituent-s each discharge at the rate of 5 barrels per hour, will cause a discharge of a. considerable proportion of one constituent with the other when the rate of discharge of one constituent is increased to 10 barrels per hour or is reduced to 1 barrel per hour,

It is a primary object of my invention to maintain the ratio of constituents held in the rotor substantially constant despite large variations in the capacity, the relative rates of discharge, and the viscosity of the constituents. At the same time the design of the rotor is no longer affected by any empirical considerations, but is founded upon the mathematics of hydrostatic pressure and centrifugal force.

By maintaining a constant ratio in the rotor, the relative periods of time during which the respective constituents are subjected to centrifugal force are maintained constant.

To explain how my invention effects these results, it is desirable to state that the relative amounts of constituents held in the rotor are determined by the fact that the hydro-static pressure of the constituents must balance at the surface where the separated constituents come in contact before they are discharged. Hydro-static pressure in a liquid subjected to centrifugal force is a function of the angular velocity, the specific gravity of the constituents, the radial distance of the contact surface mentioned above from the axis of rotation, and the radial distance flOll'l the axis of rotation of the surface where the liquid comes nearest to the axis of rotation. Itis the last mentioned factor that is so variable in the rotors heretofore designed and a variation in this factor obviously causes variation in the distance from the axis of rotation to the surface where the con stituents come in. contact, thus changing the ratio of constituents held in the bowl, changing the relative periods of time during which the-constituents are subjected to centrifugal force, reducing the eflieiency of separation, and changing the character of the results.

The point where a constituent comes nearest to the axis of rotation is hereafter termed the discharge surface of the constituent. It is evident that the discharge surface is in practice always nearer the axis of rotation than is the Weir which controls it. The difference is the depth of the crest, and for a weir of given width (concentric with the axis of rotation) and a given length (parallel with the axis of rotation) is dependent upon the rate of discharge and the viscosity of the constituent. Inasmuch as the functioning of the rotor is dependent upon the distances of the relative discharge surfaces from the axis of rotation, it is obvious that the design of a rotor in which the depths of the crests are COll'lPillfitlVGlY great involves a corresponding correction in the determination of the distances of the weirs from the axis of rotation. This correction involves so many unknown factors that the design is perforce empirical. If, on the contrary, the depths of the crests are in practice negligible, the discharge surfaces may be considure of the usual rotor to function properly I under changing conditions.

In accordance with my invention, in its preferred form, the separated constituents are discharged over annular weirs having knife edgesconoentric with the axis of rotation; the Weirs in a rotor being similar in character with edges concentric to the layers of the separated constituents to be discharged thereover so that the respective constituents shall be subject to conditions which maintain their relations throi'ighout changes in the rates of discharge or viscosities, and such weirs being provided by rings one or both of which can be changed to alter the discharge radius in accordance with the cl'iaracteristics of the constituents to be separated. But it will be understood that these changeable rings are not essential, particularly where the densities of the substances under treatment do not change, and that the contours of the weirs may vary from the preferred concentricity, improvement being effected by increasing the radii of the weirs substantially over those heretofore used.

Characteristic effects of my improvements are the production of desired crests of maximum widths and minimum depths, which do not change substantially with changes in the proportions of the constituents to be separated, the capacities, or the viscosities, and do not substantially change the radius of conjunction of the layers of separated constituents, thereby maintaining a constant ratio of amounts of constituents held in the rotor.

The characteristic features of my invention are set forth in the following description and the accompanying drawings embodying a form thereof.

In the drawings, Figure 1 is a broken section view of a centrifugal separator illustrating a form of my improvements; Fig. 2 is an enlarged broken sectional view of the top of the bowl of Fig. 1.; Fig. 3 is a sectional plan view taken on the line 3-3 of Fig. 2; Fig. 4 is a sectional View taken on the line H of Fig. 2; and Fig. 5 is an irregular sectional view through a bowl stem illustrating modifications in construction.

lhe mechanism illustrated comprises the frame 1 providing a case 2 in which the bowl 3 having the neck e'is suspended and revolved by the spindle 5 coupled to the neck,

the bowl being fed through its bottom inlet 6 b the nozzle 7 supported by the case.

Iii accordance with my invention, in its preferred form, the weirs or dams over which the separated constituents flow comprise the ring 8, having the inner narrow lip or knife edge 8 concentric with the axis of rotation and the outer edge 8", and the ring 9 having themarrow lip or knife edge 9 concentric with the axis of rotation, providing means for controlling the discharge of the constituents which have been separated in the bowl.

The lighter constituent, after passing through the ring 8, over its inner edge 8, is discharged outwardly by way of the channel 8 concentric with the edge 8' and the passage 10 in the neck 4 to the receptacle 11, the outlet channels being of such cross sectional area and distance from the axis of rotation as to offer no obstruction to the discharge over the edge 8'. The heavier constituent flows over the edge 8 of the ring 8 and through the inwardly inclined passage 12 of annular cross section to the annular channel 13 surrounding the neck 4, whence, it is discharged over the overhanging edge 9 of the ring 9 and into the receptacle 14.

The ring 8 is provided with a concentric collar 15 which forms the outer wall of the channel 8 and is adapted to be screwed on the bottom of the neck 4, permitting the substitution of rings or weirs of different dimensions proportioned to different conditions of characteristics of the constituents to be separated, if desired. The ring 9- lies within a collar 16 fixed on the top of the bowl and is held in place by a ring 17 which screws on the collar and has a flange 17 which engages such ring 9, providing for the substitution of controlling rings or weirs of different internal diameters proportioned to different conditions of use..

Wings 18 are fixed to the ring 8 and the collar 15 to provide means in the top of the zonal for imparting rotary motion to the As the edges 8' and 9' are full circles concentric with the strata occupied by the constituents in the bowl, bein placed at the radial distances for effecting the control desired, the change in the depths of the constituents flowing over such edges will be negligible or a minimum, varying unsubstantially with such slight changes as may take place in the discharge or inner surface I of-the lighter constituent and the place ofdivision between the edges 8 and 8-" of the separated constituents in the bowl.

While the ideal construction comprises full annular knife edges concentric with the axis of rotation for controlling the discharge of the different constituents, this construction may be modified within the scope of my 'bowl and which may discharge directly to the receptacles 11 and 14.

Having described my invention, I claim: 1. In a centrifugal separator, a revoluble bowl provided with means comprising outlets and weirs for effecting the dischar e of separated constituents with negligib e depths at said weirs.

2. In a centrifugal separator, the combination with a frame, of a bowl, and means for supporting said bowl vertically in revoluble relation to said frame said bowl provided with mean for discharging sepated constituents and maintaining a substantially -constant ratio between the constituent held in said bowl throughout variations in the quantities dischar ed.

3. In a centrifu a-l separator, t e combination with a frame, of a bowl, and means for supporting said bowl vertically in revoluble relation to said rame said bowl oluble relation to said frame said bowl provided with means for discharging separated constituents and maintaining a substantially constant ratio between the constituents held in said bowl independently of the viscosity of saidconstituents.

5. In a centrifugal separator, a revoluble bowl having controlling weirs substantially concentric with the axis of revolution;

6. In a centrifugal separator, a. revoluble bowl ha'ving weirs with narrow edges for controlling the discharge of separated constituents.

7. In a centrifugal separator, a revoluble bowl provided with outlets and weirs for controlling the discharge of separated constituents so that the distances ofcthe nearest points of the discharging constituents to the axis of revolution shall be in substantially constant ratio throughout changes in the rate of discharge.

8. In a centrifugal separator, a revoluble bowl having outlets and rings with edges of different diameters for controlling the discharge through said outlets.

9. In a centrifugal separator, a revoluble bowl having outlets for separated constituents and changeable weirs for controlling the discharge of separated constituents through said cutlets.

10. In a centrifugal separator, a revoluble bowl having outlets, substantially concentricrings of different diameters for controlling the discharge through said outlets, and means for permitting the ring of smaller diameter to be changed.

11. In a centrifugal separator, a revoluble bowl having outlets, substantially concentric rings of difierent diameters for controlling the discharge through said outlets, and means for permitting the ring of larger diameter to be changed.

12. In a centrifugal separator, a revoluble bowl having a substantially concentric channel and ring in combination with a passage for discharging a separated constituent under control of said ring.

13. In a centrifugal separator, arevoluble bowl having discharge passages oblong in cross section transversely to the axis of revolution for separated constituents of diiferent densitie and weirs for'controlling the flow of constituents through said passages, said weirs extending in the direction of arcs struck therethrou'gh with the axis of revolution as a center.

14. In a centrifugal separator, a revoluble bowl provided with outlets and weirs placed at the radial distances for effecting the desired discharge control of separated constituents through said outlets, weirs having approximately the largest said practicable dimensions transversely to the direction of fiow of the discharging constituent.

15. In a centrifugal separator, a revoluble bowl provided with outlets and weirs adapted for producing approximately the maximum widths and the minimum depths of crests for the discharging separated constituents.

16. In a centrifugal separator, the combination with a frame, of a bowl, and means for supporting said bowl in revoluble relation to said frame, said bowl having outlets for discharging substances of different specific gravities separately and means for maintaining a substantially constant distance between the axis of rotation of said bowl and the discharge surface of the substance of least specific gravity notwithstanding changes in the relative rates of discharge of said substances.

17. In a centrifugal separator, the combination with a frame, of a bowl, and means for supporting said bowl in revoluble relation to said frame, said bowl having outlets for discharging substances of different specific ,gravities and means for maintaining a substantially constant ratio between the distances of the discharge surfaces from the axis of rotation notwithstanding changes in capacity, relative rates of discharge and viscosity of said substances.

In testimony whereof I have hereunto set my name this 26th day of October, 1918.

I T. SHARPLES.

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