US3101313A - Hydro cyclone - Google Patents

Description

M. D. WOODRUFF HYDRO CYCLONE Filed April l, 1959 Aug. 20, 1963 of Ohio Filed Apr. 1, 1959, Ser. No. 803,435 Claims. (Cl. 209-211) This invention relates to centrifugal separa-tors, and particularly to hydrocyclones for separating la liquid suspension of solids into accepted and rejected fractions. Although not so limited, the invention has especial referen to `a conical separator, sometimes-known as a cleaner, used in paper making processes to separate clean, usable fibrous material from la flowing liquid pulp suspension which, in addition to the usable material contains unwanted dir-t and coarse particles. A device of this kind is disclosed, for example, in the patent to E. W. Samson et a-l., No. 2,377,524, issued June 5, 1945, and includes a means defining a separating chamber receiving through an inlet at the base end, the liquid suspension of solids. By virtue of the arrangement of the inlet the suspension is discharged tangentially into the separating chamber in la manner to progress from one end to the other inV-a swirling motion. The 'apex end of the separating chamber is open, 'as is the base end wherein a nozzle or .finder is located 'to receive and guide an inner vortex in which is comprised the accepted fraction of solids, the rejected `fraction discharging thnough the apex end of the chamber. VThe nozzle arrangement at the base end of the sep-aratingvcharnber is considered as providing for overllow, with underflow taking place at .the apex end. These terms, however, do not denote `attitude limitations since the separator device can be mounted in any position which is convenient from yan install-ation standpoint, the speed of movement of the liquid suspension thnough the separator making the device operationally independent of gravity. I

.l'nvrvidespread use, hydrocyolonic cleaners as described nevertheless have certain limitations, rfor example, a tendency to work at something less than maximum eiciency and -a tendency to draw lair or liquid into .the separating chamber through the underflow end where it is mixed with the accepted fraction and travels with it to the paper making machinery.

A cause of loss of efficiency in the cleaner has been known to lie in the overflow nozzle. Eddy currents form in the region of the inlet and move along the overflow nozzle :to the entrance end thereof where portions of the currents are dnawn into the nozzle and carried out with the accepted fraction and before the cleaner has had opportunity to separate out rejectable material.

The entrainment of air with the accepted fraction may be rundesirable as affecting the qualities of the pulp supplied to the paper making machinery `from the separator. Such entnainment can be avoided by submergin-g the underflow end of the separator in `a liquid bath but it has been necessary .to avoid this recourse since' the cleaner will then dr-aw liquid into its separating chamber and dischar-ge it with the accepted fraction, the result being as in the case of air entnainment a reduction in 'quality of the issuing pulp. Accordingly, the cleaner devices heretofore have been operated either with their underflow ends communicating freely with the atmosphere, `or where the exclusion of air is particularly important, means are provided to create a vacuum `a-t the underflow end so that the apex or underflow end lof the cleaner is in communication with a source of negative pressure precluding reverse flow into the sepanating chamber.

The object of the invention is to simplify the construction as well as the means and mode of operati-on of 3f,ll)l,3l3 Patented Aug. 20,1963

cyclone cleaners, whereby such cleaners may not only be economically manufactured, but will =be more eliicient and satisfactory inuse, adaptable to la wide variety of applications, and be unlikely to get out of order.

A further object lof the invention is to significantly im- .prove the efficiency of vthe cleaner and to .prevent insuction at the underflow end of the cleaner.

y It is .another object of the invention to modify the construction of the overflow nozzle to the end that eddy currents may `be forced away from the entrance end of the nozzle thus minimizing -a bypassing oW of dirt rich pulp.` f

Alt is a further object of the invention to obviate the need for-vacuum devices and the like-in preventingreverse flow at the apex end of the cleaner, the improvement the cleaner contemplated by the invention inhibiting flow into the separating chamber through the underflow end Iand enabling such end to be submerged in liquid with la corresponding increase in overall effectiveness.

A further object of the 4invention is to provide a hydrocyclone cleaner possessing the advantageous structural features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the above and other incidental objects` in View las will more fully appear inthe specification, the invention intended to be protected by Letters Patent consists of the features lofgconstruction, the parts and ,combinations lthereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, o

their equivalents.

.Referring to the accompanying drawing wherein is shown Ione but obviously not necessarily the only form of embodiment of the invention,

`FIG. l is a view in longitudinal section, 'and partly diagrammatic, of a hydnocyclonic cleaner from the prior art, showing the mannerin which eddyy currents are formed and may joinwith the accepted fraction exiting .through .the overflow nozzle;

4 along the line 5 5 of FIG. 3. 50

- ence throughout the several views.

Like parts are indicated -by similar characters of refer- Referring to FIGS. l and 2, a hydrocyclonic device of being made of a plurality of sections bolted or otherwise secured together. `Included in the shell 10 is a portion 11 having the shape of a truncated cone, the interior of portion 11 being hollow -to define a separating chamber 12 and the opposite ends of such chamberv opening through vthe base and apex ends of the cone, Furthercomprised in the shell 10 is a cylindrical portion 13 on the base end of conical portion 11 and in superposed aligned relation thereto. A back wall 14 of portion 13 closes what may be 4considered to be the head of the device, except forthe installation therein of a tubular nozzle 15. The latter is gccncentnically arranged in the shell 10 and projects through and beyond the wall 14 at its opposite ends. The

[portion of the nozzle extending la substantial distance within the shell, as, for example, approximately to the 1'7 being adapted to be connected in a system to supply thereto a pulp suspension under pressure.

The arrangement is one to introduce the pulp suspension into the shell tangentially of the walls thereof,` the continued application of pressure at the inlet causing the pulp suspension to progress from the base end of the device to the apex end in a swirling motion inducing centrifugal forces. As a result ofY these forces there is left in the axis of the device an area of low pressure creating what may be considered to be an inner vortex moving contra.

to the outer vortex, that is in a direction from the apex end to the base end. The nozzle serves in this connection as a vortex finder, its inner end extending inwardly of the shell to receive the inner vortex and to conduct it out of the shell, the outer end of the nozzle being adapted for connection in a suitable conduit to conduct the materials caught in the inner vortex to a subsequent process step. In accordance with the concept and mode of operation of the cleaner, relatively light and clean fibers from the liquid pulp suspension are gathered up by the inner vortex and lconducted out the base end of the device as the accepted fraction while the remainder of the liquid suspension leaves the device through the apex end thereof. As shown in FIG. 2, there conventionally is installed on such apex end a conical nozzle 18 constituting an extension of the conical portion 11 and termed the underow nozzle, in contrast to the nozzle 15 termed the overow nozzle. The nozzle 18 is attached to the apex end of the portion 11 in a suitable manner, as through a lock plate 19y and bolts 21 and may be enclosed as shown by a shield 22.

The construction and arrangement of parts is one to produce a complex pattern of forces especially characterized by decreasing pressure from the peripheral wall to the axis of the device accompanied by a reverse velocity effect, the angular velocity increasing from periphery toward the axis. The pressure diiferential causes movement in the liquid suspension from the outer wall of the shell toward the center line thereof, Fiber and dirt, in passing through fields of successively increasing centrifugal force, tend to slow down in relation to their inward radial travel. A dirt particle reaching a centrifugal iield which counterbalances the radial flow will be carried in this field until it reaches the exit.

The high rotative speed of the pulp suspension produces shear effects at the margins of its adjacent layers and creates a liquid free core extending the full length of the cleaner center line and containing a partial vacuum. In eect it is a passageway for movement of air. Shear forces wipe entrained air bubbles olf the fiber rand they are forced immediately into the core. The light, clean fibrous material moves with the liquid to the inner vortex.

This, as noted, becomes the accepted fraction which moves in a reverse sense toward the `base end of the device and exits -through the nozzle 15.

The pressure difference noted to exist between the outer wall of the cleaner and the axis thereof existsv also within the head or cylindrical portion 13 wherein the pressure at the outer wall of the head is greater than in the region of theY overilow nozzle 15. This results in an eddy current, here depicted by the -arrows 20, which moves from the outer wall laterally in parallel relationto the back wall 14 to the wall of the overflow nozzle where it is constrained to turn and move along the length of the nozzle toward `the inner or entrance end thereof. Since the eddy current originates in the region of the outer Wall it l carries with at a dirt rich portion ofthe pulp, and, as this attempts to pass the opening into the overflow nozzle, some of the dirt rich suspension isdrawn into fthe inner vortex and rcontaminates the relatively dirt free fraction entering the overliow nozzle.

A part of the instant inventive concept is that of a means to obviate the harm done by eddy currents by directing the currents away from the entrance end of the overflow nozzle. In accordance with such inventive concept it is proposed to modify the exterior of the nozzle in such manner as to provide an enlargement at its inner end which will deflect those eddy currents traveling along the nozzle outward `causing them to rejoin the main body of rotating suspension and avoiding opportunity for portions of the suspension to bypass the function of the cleaner by escaping Vdirectly into the overflow nozzle.

A preferred form of such a modified nozzle is shown in FIG. 3. There, a head 23 of a cleaner is provided with an inlet 24 and an overliow nozzle 25, the construction and arrangement of parts being the same as that shown in FIG. l except that the nozzle has a wall of gradually increasing thickness in aV manner to form a sloping exterior surface 26. At the inner end of the nozzle the surface 26 terminates in an' abruptly flaring curvature 27. The result, as indicated by the arrows 28 which depict the movement'of an eddy current, is that as the current moves along the exterior of nozzle 25 it is gradually constrained by the sloping surface 25 to an outward course, and, at the final Icurvature 27, positively is deflected and directed outward toward the wall of the shell and away from the entrance to the nozzle. That the eddy currents are in fact so diverted is substantiated by tests showing a significant reduction of dirt in the clean accepted fraction.

The diverting of the eddy currents in the manner described'not only deiiects dirt rich suspension from lthe entranceend of the overiiow nozzle but also introduces a new factor in the pattern of forces at work in Ithe separating chamber 12. The precise nature of this effect, and the reasons therefor, are believed to be not fully understood. The result thereof, however, is, in acordance with a further concept of the invention, to significantly limit or to eliminate insuction through the underflow nozzle at the apex end off the cleaner. As heretofore noted, insuction of either air or water frequently is undesirable so that vacuum systems applied to the underiiow nozzles are in common use. These systems, in addition to being relatively costly and bulky of installation, have been impractical to apply on small diameter cleaners. The instant invention, therefore, makes a signilicant advance in the cleaner art in obviating the need for vacuum systems. Moreover, itis a specific part of the invention to use a modified cleaner kas disclosed in combination with a liquid bath, running the cleaner with the underflow nozzle 30 submerged within a body of water 31 which arrangement has been shown to achieve a maximum eiiiciency of the cleaner. A,

From the above description it will be apparent that there is thus provided a device of the character described possessing the panticular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction Aand arrangement'of parts without departing from the principle involved or sacrificing any of its advantages.

While in order lto comply with the statute the invention has been described in language more or less specific as t0 structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

l. A hydrocyclonic device for separating a liquid suspension of solids into accepted and rejected fractions, cluding a shell providing a separating chamber having an opening at one end for discharge of rejected fractions, a nozzle having a through opening projecting into said chamber at its opposite end to define an outlet for discharge of accepted fractions, means defining a tangential inflet to said chamber at said opposite end for introducing a liquid suspension, causing it' to follow a swirling path to said one end of the chamber and induce a central axial reverse ilow vortex from said one end lof the chamber to the inner end of said nozzle entraining accepted fractions,

Vthe opening 'through said nozzle and the opening at said one end of said chamber being axially aligned, and eX- ternally projected sloping means on said nozzle in surrounding relation to the inlet thereto at its end within.`

said chamber -to deflect eddy currents, resulting from the delivery of the liquid suspension through said tangential inlet, outwardly and in paths angularly inclined to the chamber wall and away from said nozzle inlet.

2. A hydrocyclonic device for separating a liquid sus pension of solids into accepted and rejected fractions, including a shell providing a separating chamber open at its opposite ends for discharge of the respective fractions, means defining a tangential inlet to said chamber at its end having the opening for discharging the accepted fraction,

an overflow nozzle having its inlet projected within said l chamber to define the opening from said chamber for the accepted fraction, means mounted to`dene the opening from said chamber for discharging the rejected fraction therefrom, means providing a liquid bath submerging the said chamber and dene an opening therefrom adjacent` discharge end of the last named means and means on said j -said tangential inlet for discharge of accepted fractions, said nozzle being in spaced relation to the chamber wall, means defining an opening from said chamber at its opposite end for discharge of rejected fractions, said charnber, nozzle and means dening the tangential inlet to said chamber being so arranged that on tangential admission of a liquid suspension a swirling ow thereof is produced adjacent the chamber wall to carry rejected fractions through the opening at said opposite end of said chamber and accepted fractions to and vthrough said nozzle and mems on said nozzle adjacent the inlet thereto in said chamber providing an `external lateral projection to inhibit -fiow of dirt rich fractions through said nozzle under 4the influence of eddy currents consequent to delivery of the suspension through said tangential inlet.

4. A hydrocyclonc device according to claim 3, characterized by said opening from the opposite end of said chamber being defined by a projected nozzle and means 'providing a liquid bath submergingsaid projected nozzle, the means forming the projection about the inlet t-o said nozzle being operative to inhibit ilow from the liquid bath into said chamber. K

5. A hydrocyclonic device according -to claim 3, characterized in that said nozzle has a generally uniform internal cross sectional dimension and an yexternal configuration providing a gradual expansion thereof in a lateral sense toward the inlet end thereof whereby on tangential admission of the liquid suspension the eddy currents consequent thereto will be angularly deflected to the wall of said chamber and from the inlet to said nozzle within the chamber.

References Cited in the le of this patent UNITED STATES PATENTS 2,098,608 Berges Nov. 9, 1937 V2,518,084 Smith Aug.v 8, 1950 2,757,582 Freeman Aug. 7, 1956 2,781,907 Fontein Feb. 19, 1957 2,913,112 Stavenger Nov. 17, 1959 c FOREIGN PATENTS k376,555 vGreat Britain July 14, 1932

Claims (1)

1. 3. A HYDROCYCLONIC DEVICE FOR SEPARATING A LIQUID SUSPENSION OF SOLIDS INTO ACCEPTED AND REJECTED FRACTIONS, INCLUDING A SHELL PROVIDING A SEPARATING CHAMBER HAVING AN INLET FOR TANGENTIAL ADMISSION OF A LIQUID SUSPENSION, A NOZZLE HAVING A THROUGH OPENING MOUNTED TO PROJECT IN SAID CHAMBER AND DEFINE AN OPENING THEREFROM ADJACENT SAID TANGENTIAL INLET FOR DISCHARGE OF ACCEPTED FRACTIONS, SAID NOZZLE BEING IN SPACED RELATION TO THE CHAMBER WALL, MEANS DEFINING AN OPENING FROM SAID CHAMBER AT ITS OPPOSITE END FOR DISCHARGE OF REJECTED FRACTION, SAID CHAMBER, NOZZLE AND MEANS DEFINING THE TANGENTIAL INLET TO SAID CHAMBER BEING SO ARRANGED THAT ON TANGENTIAL ADMISSION OF A LIQUID SUSPENSION A SWIRLING FLOW THEREOF IS PRODUCED ADJACENT THE CHAMBER WALL TO CARRY REJECTED FRACTIONS THROUGH THE OPENING AT SAID OPPOSITE END OF SAID CHAMBER AND ACCEPTED FRACTIONS TO AND THROUGH SAID NOZZLE AND MEANS ON SAID NOZZLE ADJACENT THE INLET THERETO IN SAID CHAMBER PROVIDING AN EXTERNAL LATERAL PROJECTION TO INHIBIT FLOW OF DIRT RICH FRACTIONS THROUGH SAID NOZZLE UNDER THE INFLUENCE OF EDDY CURRENTS CONSEQUENT TO DELIVERY OF THE SUSPENSION THROUGH SAID TANGENTIAL INLET.

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